I don't see what about it offends you so much. I've played both series in the past, and while I think Smash is a fun distraction, time killer type of game, I don't feel like it has the "meat", or depth if you prefer, to have lasting appeal for me personally. Smash is the kind of game that I'll rent, play around with for maybe a week, a few hours a day, and send it back to Gamefly when I get bored. RDR2 is the kind of game that I will buy, marathon it on release, then replay it several times over the years, just like I did with the first RDR, which is my #1 all-time favorite game. If you prefer Smash that is perfectly fine, but my opinion is just as valid.
Calling Smash a "fun distraction, time killer" type of game, because it's not. Sure, maybe that's how you see it, but for millions of people, Smash is a way of life. It's obvious you are the kind of person who enjoys single-player games, because you seem to judge Smash solely based on its single-player appeal (on which terms of course it's nowhere near as good as RDR, because it's not meant to be), so it kinda makes sense you'll get bored of it after a while. Matches against CPUs can only be fun for so long. But as a multiplayer game, Smash has always had an immense wealth of content with rather deep gameplay, making it essentially everlasting for people who delve deep into it.
I haven't played RDR, but there are many single-player games I can marathon for 8-hours once or twice. It's awesome. Smash, though? I probably played it for 8 hours straight (or more) with friends dozens of times, and it never gets old. That's the beauty of multiplayer games - they can allow for endless possibilities.
Also, the amount of content delivered with each Smash release has grown exponentially since Melee (except exclusively single-player content in Smash 4, which was lacking), and Ultimate doesn't change that. But implying Smash has no "meat" when it features possibly the largest fighting game roster ever (and certainly the most impressive one), over 100 stages and 900 songs, besides loads of different modes for both single-player and multiplayer, yeah... no.