The problem with the Vita memory cards wasn't that they were proprietary it was that they didn't do anything an SD card couldn't do and cost more.
Let's see if you wanna expand the storage on Xbox all you gotta do is pick up an expansion card and slide it into the slot in the back of your Xbox.
If you want to expand the PS5 storage, you have to look up the required specs for the SSD, price out different SSD's, check to make sure the SSD is actually performing well in the PS5, and then finally look up how you actually install the SSD into the PS5. Seems pretty complicated to me.