yeah, that and more modern netcode Multiplayer like with Q1 and Q2 and you could see a really active multiplayer community around it.
There's already quake mods that make the netcode modern and very playable. Quake3+ is the main one that is available for anyone to make servers with, but there's also Devotion, which is an adaptation of ratmod from Open Arena to quake3. Works pretty well as far as netcode goes, but it's still in development so it had some quirks in other places.
The problem with Quake3 isn't that there's no good way to play it and therefore no players. The 15$ version on steam is kinda a scam since you can play it for free if you just get the pk3 files from someone, and then there's a bunch of improved engines like ioq3 or the q3+ launcher to run it. The biggest problem with quake 3 is that the community are complete fagots who give off a peaked 20 years ago vibe which turns alot of new players off and they don't stick around and/or it's really hard for new players to actually find a place to play because the admins only let their friends advertise their servers in the main general hubs where new players will end up. There's some cool dudes in it, but there's also alot of complete histrionic cunts or really passive aggressive cunts with ulterior motives and unfortunately, those are the people all in administration positions for the main discords or forums.
A friend of mine has been running vanilla Q3 balance Q3+ servers for over a year now, has hosted multiple events, has done commentary for other communities events for them, and has done casual exhibitions to try and drum up more engagement with the community or new players, and the admins in the main discord still will not let him put his Q3+ servers on their server list, despite them being the only vanilla balanced Q3+ servers in EU and they have a small group of people who actively play on them and want more people to play. They won't give him a role for when his servers have players running games, and they won't let him advertise his discord, meanwhile, the people in the "unfreeze/fpsclassico" servers get all of those things and privileges because, ohh look, they're also the admins of the general Q3 discord where most new players will go first to see if the community isn't dead. And look at this, every server on the advertised list is empty and dead, except these fpsclassico servers. Wow, they must be the only good servers around. It's a fuckin' joke.
It's not much better here in the US either because most US servers are either good with 0 players, or have players and the server is good, but the admins have been caught cheating in the past as well as letting people they know get away with cheating, and if you call them out and show proof that they're cheating, they ban you from the servers. Or it's a server that runs well, but has bots on it pretending to be real players with non-bot names. The community is a fucking joke, which is a shame because Q3 is really fun and with the right mod, has better netcode than QL and is more customizable. Sorry for the long rant, I just don't have anyone to complain about these things to because everyone in EU already knows it, and you get banned from the notable communities in the US if you call them out on their faggorty. Makes me angy