Stadia is a garbage platform, and one new 2020 game that sees Stadia as the place to be over two 2013 consoles is probably going to be it's peak moment, superceding the previous high of "better than Atari Box".
It isn't the last gen platforms alone though. Stadia performs with much more stable framerate and more often at the ceiling of the dynamic resolution than PS5 and Series X. Faster texture loading make the visuals smoother. And it has the option to choose between performance and visual mode, the PS5 is missing.