I think preseason ranked matches shouldn't exist

This isn't a "my placements sucked" thread (I've played since CBT, and placements have always been hell since S1), but with preseason holding your MMR into the new season, it is incredibly jarring to make great strides in your MMR (back to Diamond in my case) and then quite literally the next day getting placed into plat 3 because of how crazy your mmr range shifts in those 10 games.

It's not like the state of the game changed in a meaningful way to warrant that sort of mmr change from this last patch to the season start patch. This is where I find the problem with preseason ranked. I feel as if it would be way less aggravating if it didn't exist in the first place. I could understand being, let's say, plat 4 or something at the end of S7, and then there's a gap in ranked from then to the start of S8 and getting placed into G5-G1 because the state of the game has changed massively due to preseason always introducing so many new things to the game. That makes sense. It could be that you were did excellent in one meta in ranked, but then poorly performed in another meta due to your playstyle and you have to work your way back up while you adjust to the new mechanics.

So for example, with preseason, I played quite a lot of ranked games during this time after decaying into gold last season from plat 1 or 2 due to inactivity. I got back into diamond right up at the end of preseason, about 2 weeks before the start of season 8. That's a large sample of games for the matchmaking to determine my MMR and matchmake accordingly. Then, seemingly arbitrarily, season 8 starts (with probably one of the most sparse patches I've seen in a long time) and I get thrown into placements. 10 matches is all it takes for matchmaking to decide I'm going to get placed in plat III after some rough games. This seems so counter intuitive with the concept of even having a preason with ranked matchmaking.

tl;dr It's weird to have your mmr adjust 300 points within one day because of how preseason mmr shifts into the next season. It would be less jarring if there was no ranked matchmaking during preseason, and then reopening ranked at the start of the next season. Placements feel like an inconvenience for those who played preseason than a fun/interesting way to see how your skills have changed since the previous season.

(also sorry if this is written poorly, I'm exhausted)