The instances could switch to different software, but the alternative software has to exist first, which is why it would be good for the Fediverse to see some good forks and totally different platforms too.
I really wish heaps & heaps of peeps would move to #Friendica, coz then i could also return to that as my daily default. It has so many advantages over Masto, but alas each time i spend time on my instance there, i sooner or later return to Masto coz...
...historically Masto was my first #Fediverse experience, & so that's where the majority of my interlocutors are. Most of them don't understand alternatives like F, which does many things differently to M, such that from many Mastodonners' PoV my posts thereat can seem weird, due to the different protocols, features & functions. That problem would become far less important if heaps more peeps were also on F.