I feel like it's the servers, considering for the longest time I couldn't even connect/find a lobby. Since that's been fixed I get some really bad lag, and I consider my internet quite decent.

I've noticed this too and i have a few theories

well in 2010, there would have been many many servers hosting this title, and they most probably would have reduced the number of dedicated servers when this game died off, now a lot of people are back and they haven't compensated for the new numbers

Or, has the game always been like that? and now we have adjusted to newer, better games that we expect this high quality every time and we have only noticed how poor it was now we have gone back. i think the saying "you never know what you've got till it's gone applies here"