I fully agree with everything you said.
My brother went 5 out of 10 and ended up dropping from Gold 5 to Silver 4.
I went 3 out of 10 and dropped from Silver 3 to Bronze 2.
Riot claims this season was a "soft reset" and that we would "probably end up a little lower than last season" but everyone I've spoken to has dropped almost a full league, if not more. Now I'm stuck in Bronze because I'm a support main and you can't goddamn carry from support.
I worked my ass off in Season 3 in an attempt to reach Gold for the Elise skin, but an unreliable internet connection, a full time job, and a last-minute move all made that impossible, so I ended in Silver 2. Did my promos again in Season 4, ended up in Silver 4 - the kind of "slightly lower" they're talking about.
I've since introduced friends to the game, played with them a ton, gotten a LOT more experience than I'd usually get, and yet some bad luck in my placements (including an honest-to-god 3v5) means I drop to fucking Bronze?
To some extent, it's fun to climb the ladder. But artificially dropping my goddamn rank just eliminates all the hard work I did to get that far. This is not a game I'm naturally talented at. It's a game I play because it's fun, and when I want to improve myself, I put in a LOT of effort. Now all the stuff I learned about carrying Silver - directing your team, positioning, working together in teamfights - is completely moot because my Bronze teammates ignore me and I need to somehow win games alone.