So, yes, Crossplay seems to be an option. When I open 'join players'. I see more than two dozen games going at any given time, all which can be joined in on. SteamStats shows an average of active players being between 1,000 - 1,500 daily. (this does not include consoles)

To be clear; I've never joined into any multiplayer game outside my own as I always have a group of 3 that wants to play. We went through the story, all side quests, then even farmed out end game stuff to min max and ran the end game hunts as a group. So as to the quality of the group, I can't speak upon.

does it have a lot of players playing? I see its on PS5, and xbox meaning more players. Is cross play on?

Yep, up to 3 people. Really great Coop, RPG, highly recommended.

this game has multiplayer?

Another win congrats