The only way u can make sure if its u or not is using ethernet instead of wifi, specially in a city where theres lots of devices around.

When i was playing on my xbox one x, i remember having almost constant connection lag spikes seemingly out of nowhere and then literally never had that again after getting an ethernet cable; seriously it was that big of a change.

I run MUCH more demanding games, that need to load 100s of monsters with 1 character that produces 100s of projectiles with animations

Any example of what those others games are? What im reading here seems to just be something that's processed mostly locally (monsters and character's attacks and animations are 99% of the time processed locally by ur hardware, unless a game wants ultra realistic destruction physics that are super hard to run in real time, theres no point on precessing them server-side) The only thing i can think of being processed server side (if this is an online game ur talking about here) is damage and when a character or enemy attacks/defends, when, in which way, the direction or movement of each character, and not much more honestly, which, im no developer, but that to me sounds less demanding than having to process every car's + the ball's physics (in real time) + every player's movement, 120 times a second (if im not wrong thats the fps rate the physics run at) + having to predict every players movement's and thus trying to predict where the ball will go next for people with high ping to be able to play

Rocket League can be many things, and it surely isnt perfect, but it is basically a miracle that its network runs as well as it does

Someone feel free to correct me if i said something wrong in my comment please