When I join a server, the current match you know, the 2 players' color/model were set to default skin for some reason. It's been happening for a long time, but I don't know if anyone has noticed. Please fix this bug, and also, the current moves and position were incorrect, also the currently playing match frame were set to its original frames.

Fix this please! I'm RAGING!!!

The entire reason is because you weren't there for the entire match, so you haven't seen all the frames. Naturally, if you have half a replay, it's going to be glitched, and there's no point in storing all that data on the servers so that when you join a server mid-game you can see the entire match. Would take up ridiculous amounts of storage considering how many matches go on and how large some file sizes can get.
As with player customs, they don't refresh every 30 seconds because that's stupid. Player customs refresh at the start of every match, where the client dls the players customs who are playing atm. That's why sometimes you get a second or two of lag when a new match starts because the client has to dl a shit ton of textures and flames and stuff.

It's really not that big of a deal, you joined mid-way, you obviously won't know what happened during the 100 frames you missed, unless it's a spar. Then again, there aren't as many long tf lobbies as there are short tf lobbies, and who really cares about seeing someones set for 30 seconds, you can just /lp them if you're that desperate.