The true number of playable games is of course much higher, but this is still an impressive milestone.
For comparison: the Nintendo Switch has roughly 4500 games available for it, the PS5 has about 500 games (+ 3500 PS4 games), and the Xbox Series X/S have 400 (+ 3000 Xbox One games).
Don't forget the deck emulates a lot of other console, and therefore, the number of game you can play should also include those, I emulate the switch on my deck and it works like a charm.