Warframe, but it's a co-op game rahter than an mmo. Darkfall did, but am not sure if it still does. Moratl online, but I've never tried so can't say what it's like. DDO has a mixture of both. There's also STO which sort of does but not really.
Personally I would prefer a proper starfleet command online. Multiple factions, component targeting, convoy raids and defences, maybe even territory control(if done right or at least balanced out with npcs for the less popular faction).
I think this is the closest you'll get to finding out the actual population if that's an issue(remember there's nothing below light) But the best opinion I think you'll get would be yours i.e. since it's now freeish why not see for yourself?