They made some impressive technical achievements, but their overall platform and infrastructure was awful. For example, no unified friend system, different online services for different consoles, no SSO for games.

I think for casual play like Mario Kart, Pokemon, etc, it worked fine. It absolutely hamstrung more complicated efforts like Smash, Metroid, and third parties were forced to all heavily build out their own infra or not build the feature at all.

These were problems that plagued much more powerful systems (Wii, 3DS - until very late in the lifespan of the console, Wii U, and even the Switch)