First time I'm posting on here with regards to preseason, oh boy.
Personally, I find complaints with regard to "stompy" and "snowbally" games to be perfectly fair. It certainly doesn't apply for every game, but I've noticed it in a lot of the games that I've played. When one team begins to get little bit ahead, they snowball very quickly as of preseason. Make no mistake, they had the potential to do that before, but it's much more common now.
This doesn't apply for everyone (in fact, a thread glorifying the preseason's faster games is currently trending on the League subreddit), but personally, I prefer the air longer games with more comeback potential. I relish in games with unexpected but incredible comebacks, or very even matches that can go to either team. That's why LCS fans often like it when a best out of 5 match goes for 5 games. The matchup feels so much more even, like there's room for the victory to go to either side. The same applies for us normal League players. Many of us (though not all) want to have comebacks be possible. When I'm in a match, even if I lose, if the game was close, I still usually have fun. In a game that ends up being a total stomp, you don't feel like you have the potential to make a comeback, and the game feels much more tense and exciting.
Yes, the game may be fixed before the season start, but that's why it's important for people to make threads voicing their opinions. If no one said a word, then Riot wouldn't feel a need to change up the game before the season begins. I agree that a lot of the threads a rather redundant and some can be a little garish, but at the end of the day, many of their complaints are legitimate. We want a fun game, and the only way to achieve a fun game is to make it please the community to a large (though obviously not absolute) degree.
A point that you made that I agree with - if you don't enjoy League, don't play it until preseason ends. Yeah, I can agree with that. Like I said before, I'm not enjoying the preseason update that much myself, so I'm not planning on playing all that much this preseason. Regardless, I think it is important that people voice their opinions so that Riot has a chance to improve the game for when the regular season begins.
tl;dr: We don't want to be try-hards, we want to have fun. But right now, the vast majority of players don't find League to be as fun as it was... which is why people have threads explaining these issues. There's nothing wrong with that.