Software wallet MyCrypto discontinued by author, it uses a keystore file/password system. Is there any chance funds stored that way will become inaccessible due to updates in eth protocol?

I'd feel a little safer if I was using a paper-storable seed phrase, rather than this keystore/password system that I don't fully understand. But if people who know eth better than I do say it's not the sort of thing that protocol updates would break, then great.

My biggest problem with this, is that I don't think I have any way to ever access my funds without going through this now discontinued app, due to this keystore system. Whereas if I use a seed phrase the wallet client shouldn't matter at all. But if other wallets use this same auth system in that case I also have nothing to worry about.

I kind of want to just forget about my crypto for the next 20 years, so looking for long term storage solution, but not interested in buying a hardware wallet.