It is a shame that, even today, none of these Commodore or Amiga ROMs are open source, or even free to use/distribute.

They're easy to find if you want them. If you ever owned any of the relevant machines, then I'd say you're even morally in the correct. Feel free to send Commodore or Cloanto some cash for your use if you feel so inclined. Cloanto even offer packages for both C64 and Amiga that include the most relevant ROMs (and Workbenches, in the case of the Amiga).

It's obviously inconvenient but I wouldn't call it "a shame". It's historically quite normal, open source/free to use just wasn't a common thing back then.