Once I finally get a Series X, I'll have owned every major console from the past five generations except for the Saturn (it was discontinued several months before I got my first job). I have had my fair share of both praise and complaints about all of the current Big Three. Perhaps because I've always been a multiplatform person since the 16-bit days, I've never really understood how vociferous people get over their like of a particular brand and, frequently, dislike of other brands. I know where it comes from: the same part of the brain that all other forms of tribalism comes from. Still, why tie your own identity as a person to a particular brand of electronic toy? It's not something serious, like disagreements over matters of public policy.
I think a lot of it has to do with this:
Once I finally get a Series X, I'll have owned every major console from the past five generations except for the Saturn.
Not everyone has money to spend on getting every console under the sun. For starters, pretty much every kid or teenager that wants a console will have to ask their parents to buy them one, and the vast majority of parents won't buy more than one. Obviously, this stops being the case amidst adults, but inevitably you already have some brand loyalty forming in someone's childhood years - heck, the gaming marketplace was very much meant for kids during the 80's, 90's, and even a little into the 2000's. Games were seen as a kiddie thing, so you didn't have many adults to begin with.
Even ignoring that and taking it from the point where there are many adult gamers with jobs, there are a lot of people who don't make enough money to be spending so much on games. You can argue that if someone makes enough to buy one console, they can eventually buy another, but for most people it's just not worth it as it can be really redundant to own multiple consoles just for a few specific exclusives. This obviously also depends on where you live, I'm sure in somewhere like the United States there might be plenty of people who make enough money just fine but somewhere like here in Brazil it's extremely expensive to buy just one console and the vast majority of people wouldn't even entertain the idea of getting another.
And, yeah, if you can only get one console for financial reasons, it is still very much possible to not act like an idiot and take sides like the console brands are your football team. But I feel that's just how it is. Inaccessibility makes people want to disregard what they can't have, and for some this can escalate into idiocy. This is especially true if it's between kids at school, who love to take sides to argue about stupid things and bully the ones with unpopular opinions - and since most gamers in the 80's, 90's and even a bit into the 2000's were kids at school, well... there you have it.
Maybe I'm not looking in the right places, but as gaming lost its stigma of being a kids hobby over the past 15 years or so, I feel like console wars have become less and less relevant, to the point I rarely see anything of the sort nowadays.
I do have some brand loyalty for certain things, namely some food items. I like Coca-Cola best out of all cola brands because I think it tastes the best. But I don't tie my identity to how my taste buds perceive a particular brand of soda. I don't particularly like Pepsi (I'll drink it if that's all that's available at the moment), but I won't begrudge others for preferring it over Coke. And when it comes to non-foods, I honestly can't think of any brand I'm loyal to to the exclusion of all others like it.
I think my lack of brand loyalty for consoles stems from pure historical accident. In the late 80s I was all about Nintendo. Elementary school me thought the NES was the coolest thing ever. I was all about Nintendo at the time. I had a subscription to Nintendo Power. I had a Super Mario lunchbox. But to be fair Nintendo really was the only name in console gaming in the latter half of the 80s because of their de facto monopoly on the market.
Needless to say, I was super excited to get a Super Nintendo when it came out in 1991, but instead my parents bought me a Sega Genesis, which I knew next to nothing about (the only reason I even knew of Sega was Sears catalogs). I think they did that because the Genesis was $50 cheaper than the SNES at the time ($150 vs. $200) and they probably thought "Eh, he's 11. He'll like it." Well, as it turns out I did like it, though I still really wanted an SNES. Fortunately I had other ways of scratching that itch until I finally got an SNES in 1994. While back then on up to this day I prefer the SNES to the Genesis, I spent a considerable amount of time playing on the latter, and I'd still consider it worthy of placement among my Top 5 systems ever. But the SNES was the last time my parents would buy me a system, and my mom flat-out stated that if I ever wanted another system I'd have to wait until I got old enough to get a job to buy one on my own, which I eventually did.
With Sega struggling post-Genesis, in my early high school days my attention for Gen 5 systems was squarely back on Nintendo. My best friend of almost 25 years bought an N64 right around the time it came out, and I would come over to his house (which is my house, now) throughout my sophomore year to play Super Mario 64 and Mario Kart 64. While I was aware of PlayStation due to gaming magazines covering its games, it wasn't until Final Fantasy VII was announced as a PS1 exclusive that I actually became interested. When I did finally get a job in 1998, mere days after my junior year ended, one of the first big purchases I made was for a PS1. I figured I'd go ahead and get one to play FF7 since my friend had an N64 and I could just play it at his place until I could get one of my own a few months later. While I did end up getting several other games for the PS1, I still had a clear preference for the N64 because most of the games I was interested in were on it.
As you can see, I always have had preferences. I preferred Nintendo throughout the 90s (and I still really love their games; the Switch has some of their best output since the 90s). I didn't really have a clear preference in Gen 6 (it was the nadir of my video game playing), but since Gen 7 I've preferred Xbox over PlayStation for "conventional" consoles. But even if a system wasn't my favorite, I always felt every major console had enough to offer to warrant getting one at some point.
Now that I'm done with my gaming life story, I can say that I do understand that not everyone was able to have multiple systems per generation growing up. I can't imagine many kids living in the early 90s had both an SNES and a Genesis. And I do get why some people may never decide to branch out into other console brands as adults. They may be perfectly fine with the brand they've been playing on, and they may even not have the time and/or money to invest in other brands (I've never had a lot of money, but I'm good at saving it, plus I bought most of my hardware with tax refund money).
Still, I don't get how people get personal over these things. For some people, it's not enough to like a brand. They feel they need to defend their chosen brand against any and all criticism (real or perceived) or even against anything that's not glowing praise and exuberant optimism. They feel the need to attack other brands as "inferior" regardless of actual quality. We see it with all fandoms. Star Wars vs. Star Trek. DC vs. Marvel. And of course Nintendo vs. PlayStation vs. Xbox. Even within a given fandom, you see internecine warfare between fans who fight over what parts of the franchise they should or shouldn't like (there's some people will treat you like dirt if you so much as dare to defend the ST sequel trilogy in their presence), or certain fans going beyond the bounds of acceptable adult behavior in attacking the owners of the brand for doing things the fan doesn't approve of (and I'm not talking about legit mismanagement from the owner; I'm talking about even things like creative decisions the fan doesn't like). For that reason, I disagree that the "console war" mentality is not still relevant in gaming communities. I see it in forums all of the place. There are still people that feel the need to attack brands they didn't like or get overly defensive of brands they do like, video games or otherwise. Now, it may be on the decline (surveys indicated greater PS-Xbox cross-ownership in Gen 8, and I think the most recent survey of Switch owners also shows most of them own a PS4 and/or XBO), but it's still far from rare.