vrchat's playerbase, I estimate, (based on trends I see daily in public worlds) is actually growing significantly.
It's hard to chart this, though thanks to Oculus Quest and Oculus Desktop builds of the game. To be clear however, the game has not dropped below 5000 concurrent players on steam alone at all, ever, with commonly around 9k peak averages daily since January 2018.
This is crazy for any "small" game. Absolutely insane. This makes it a SMASH VR HIT beyond almost all others according to steam's metrics, and the 66th most populated game as of today on ALL OF STEAM, let alone SteamVR, (#1 in vr return usage and total playtime by a long margin for most I imagine) and I estimate somewhere around half the userbase that is actually using vr hardware isn't even using steam itself, they're using oculus home or quest. Plus, some people don't even know it's supported on desktop thanks to the name alone! It's an extremely niche "game" that has hit 23k+ concurrent users on occasion.