Nintendo has always released enhanced ports in addition to BC. For example, if you get Link's Awakening DX for GBC, that is not a $30 charge to play LA on GBC using BC. You can simply put the original non-DX cartridge in your GBC and play the grey version. There is no additional charge to use the BC feature.
Can I imagine a world where there is a new Switch 2 exclusive version of Zelda TotK, AND the system plays the original using BC? Absolutely!
Almost every gen that Nintendo had the opportunity to do so, they offered physical BC, ie GC to Wii, Wii to Wii U, GB to GBC to GBA to DS. It so happens that Switch uses a different form factor, architecture AND media than Wii U, which also sold like shit, so yeah, this time the closest thing we had to BC was just dumping Switch ports everywhere, but that's still not charging for BC, it's just releasing a game on a different platform.