Hey there, I agree, replays are really fun.
Unfortunately, replays are also not very stable. We used to have them enabled in the past (a long time ago now), and performance wasn't good.
Still, I want to try to add replays back at some point, see if Valve made some improvements. However, I have other more important changes on the list I want to do first, like new custom maps. Adding replays is also quite tricky, so I don't want to rush and break everything