So, I can explain what is going on at the moment.
Firstly, positional ranked has screwed up a lot. It has created a new level of emergence that Riot never prepared for. In addition, LP gains have been absolutely whack. These two alone may cause this system to be reverted, but we're not done there.
The game currently is about high damage, high rng. Add random players to the mix, in addition to the chaotic nature of positional ranking, and you have more wild games than before. Now, you have less of a chance of influencing if you win games or not. It shows mostly if you watch pro streams of people smurfing or simply trying to climb through diamond. The game can be over by the weakest link rather than by the strongest carry.
This is perhaps the flaw of solo queue, and why I've said for years now that either solo queue be removed, or Riot simply focus all their balance and design decisions on competitive play. Cause at the game's current state, they are not capable of delivering a stable experience or foundation that the game can stand on. I could write all day all the changes they could do to make the game more stable again, but like all the people before me, it's useless in the face of Riot trucking forward and doing things like small incremental stat changes to their champions, forgetting to nerf certain ones, buffing random ones, and just outright having to guess most of their design decisions.
One last thing, I wish we had the old design team back. They knew some semblance of how to balance things.