How to fix lag on steam?

Hi everyone! Been a long time fan of AOE, played a lot as a kid and got back into the game. My girlfriend and I play together all the time via steam, and just recently we've been having waves of unbearable lag. The game worked perfectly fine a week ago but now our ping shoots up to 15k+ at times. We live close and have no lag on any other game,calls,video chat, anything at all.

If it's because of the steam client, does that mean if I move to voobly I'll have to buy the game again? I don't know what to do. For the last few months our favorite thing is to play AOE together against some bots but we can't do that now. Any help would be greatly appreciated.