Why would you ever expect a service like this to be free in perpetuity? It's hardly a bait and switch: you never paid for anything, and still got 15+ years of service!
[1] https://web.archive.org/web/20110429023658/http://www.google...
Of course, Google later removed this clause from the ToS.
The only valid argument for it being legal to discontinue this on you is that G-Suite is not GApps, and both are discontinued services anyway, with Google Workspace being the current offering. Which is presumably what they would argue if sued over this.
Looks suspiciously at Google docs, which is free, rapidly approaching monopoly status if it's not there already, and has no revenue stream for personal users to speak of.