The bolded is something I don't think I can ever possibly agree with. A good studio track record tells me what I'm likely to expect, and knowing the source material doesn't go in an unfavorable direction will have a direct impact on how much I enjoy the anime I'm jumping into. I'd agree that there are nuances you can only glean from watching the actual show, but to consider all background information useless is severely oversimplifying it. Personally I'd say basing an opinion on a single episode is insufficient...but to each their own I suppose.

I'm sure there are plenty of well-written anime out there that I never bothered with due to the theme, but I honestly don't see how can I enjoy something when the foundation of the story is something I absolutely don't care for. 

Quality isn't objective, after all, at least in this context.

Some of my favorite studios have produced unbelievable shite. Animation studio and not even the director are stable attributes to judge the likely quality or enjoyment of an anime, hell not even direct sequels. Your comments tell me that you haven't even tried to step out of your comfort zone. I was once that way too, disregarding everything that's not immediately appealing. I've missed so many great animes because of this and instead watched the dreck that was supposed to be "my kind of anime".
Well, I can't force you, but broadening one's horizon usually turns out pretty well. It's not like there is much to lose.

Just an example. I always avoided any anime that centered around idols because I found the concept behind it absolutely bullshit. Then I gave Love Live a chance and it was pretty good. Yet I still dismissed every other Idol anime because I didn't think others would be that good. I was even arguing how Love Live was so much better than Idolmaster even though I have never even seen it. I based this simply off the bare information I got from the internet.
To prove my point I started watching it. And it was glorious. Not only was the main series unbelievably enjoyable to watch, after it I could even enjoy Puchimas, which is one of the best comedy shows I've ever seen.

So yeah, judging an anime by its cover is always a bad idea. Unless you don't want to experience different things.

For me, it's pretty much what Super_Boom said. I don't like watching a lot of animes at the same time, i do some research before i watch something  and i also dont like ecchi, harem, fan-service anime so that limits my options and i usually end up with 3-4 series per season.

That's the attitude that makes people miss master pieces like Madoka and Yuuki Yuuna.

I watch--or if it's really bad, skip through--the first episode of just about everything. Some anime I feel confident I won't enjoy so I drop them immediately. Others get a "maybe" rating and I keep watching until I've seen enough to reach a conclusion.

More often than not, "maybe" anime never ends up clicking with me and I simply stop watching, sometimes without ever thinking about it. I'll put off the latest episode and just never get around to watching. I've seen enough anime to know that the first few episodes can sometimes be misleading, however. Punchline earlier this year, for example, which I thought was going to be vapid but instead turned out complex and interesting.

To each their own, though.

Personally, I generally dislike generic anime and anime with poor writing or a dependence on tropes and cliches. An abundance of those can lead to me dropping something unless it makes up for it in other areas. I'll admit that a really good character can sometimes keep me hanging on.

I just click on shit and watch it. I'll give most things a chance if the basic concept is at least vaguely interesting. There are some things I know I won't like, such as the vast majority of reverse harem anime since that just isn't my thing, but I'll give a lot of things two or three episodes at least unless the first episode is just absolute garbage.

I also cross reference some MAL rankings, mostly just to make sure I'm not clicking on something universally despised. Like most ratings, I hardly consider their judgments flawless, but they help to narrow down my options a bit with the copious amount of content out there.

I do have my preferred genres, but, I mean, I even gave a musical moe anime with shitty CGI about six episodes before dropping it a couple seasons back, and that's a far cry from what I usually watch. I didn't even stop because of the genre. It was just shitty.

That's true. I didn't watch madoka at first because of that. But i think great anime like that are very rare so people will keep talking about them for a long time and you will eventually find out about them. I also wasn't interested about Yuuki Yuuna but everyone kept saying how awesome it was so now it's on my watch list.

So much yes, I love those two so much.

Normally i would agree but if you havent watched Madoka you're making a big mistake.

Psh, magical girl is fine. Not so long ago, I was watching Fate/Kaleid and Cardcaptor Sakura. I feel like I watched other ones within the past six months too, but I don't maintain a list of what I've watched anywhere, so, ya know, whatever.