@HOSCHMOSCH I'm sorry to hear you have this issue. I am not an expert but as far as I know, there have been no recent changes to the networking aspect of the game.
Here's what worked for me, to avoid lag:
Using the network info in-game (visible in the top right when you press F11), you can see which players have bad connections to each other and avoid games with them, by hosting your own lobbies. This network info panel looks like a black table and will show when player X stops receiving data from player Y. It's usually enough to exclude one of them to get rid of the lag.
If you want, you can also try smaller games. The chances are much, much better for a smooth experience, even in a 5v5, compared to a 6v6. I know it's not the same, but maybe it's still fun enough? As a small consolation, at least the lobbies will fill faster.
I don't know how your games lag in detail, and I don't mean to suggest that it's probably you, but just in case this is something on your end, here are some other things you can do: If you often lose connection to all players at once, and you are using WiFi, connecting your PC to your router with a cable will probably fix it. If you see a lot of small numbers in the row with your name on that black network info table, that might be a sign that something is wrong with your home network or internet service. Contact their tech support.