Sony themselves said the game was a hit in their eyes. People were so desperate to make every PS5 exclusive seem like a sales bomb because Xbox simply didn't launch with or had any exclusives for a whole year.Don't fall into the FUD like certain folks who still believe Rift Apart only sold 1 million copies on PS5 and lost money until it got the PC port (both of which are patently false).
I wouldn't be surprised if Returnal has hit at least 1 million by this point, and no matter how you look at it, the game's still Housemarque's biggest success commercially. It's also a new IP in a genre that isn't exactly mainstream. The game is successful.