Here's another one where it was just wrangling a crazy player

In between those two matches I lost 6 in a row, felt terrible
Question for better players: How do I tell the difference though, like when to play fast or slow vs a player? Like how do pros and high MR streamers know when they can just be dumb and not ever adapt their game, and when someone is clearly on point immediately so they know to play neutral?
I'm really confused, ranked for me seems like I just steamroll a player or get steamrolled by an absolute god who for some reason is at 1500MR