At this point people have loved the PS5 and Xbox Series for having full backwards compatibility. The Xbox goes even further through software. People liked the Wii’s backwards compatibility and the Wii U (for those who had it).
And Nintendo’s long chain of BC from the GB to the 3DS (though eventually dropping GB/GBC) was legendary.
The Switch was such a leap over the 3DS and WiiU Nintendo got away with it. It’s had such a long life having no BC could be a huge hit if the Switch 2 didn’t have it.
I think all three intended to try and keep it going forward at this point.