But on Smash there are lots of characters from very old IPs that nobody give a damm any more. There are also lots of secondary characters.
Besides smash is cartoon and Nintendo has lots of cartoon characters for it, unlike Sony.
What are you talking about? Nobody gives a damn about Donkey Kong? Or Kirby? Or what are you talking about? PSASBR included so well-known IPs like Ape Escape, Starhawk, Sly Cooper or Fat Princess. So fair to the par to games like Earthbound and Ice Climbers.
And Sony had no problem to include Kratos and Nathan Drake in PSASBR, so these aren't cartoony at all, so seemingly that is no problem.
After all Smash Brawl had 39 playable characters and four years later PSASBR only included 24 characters, even including DLC. Two years later Smash 4 included 51 characters and 7 DLC-characters.
So yeah, Sony has much more difficulties to whip up recognizable characters from different IPs than Nintendo.