> There's an unfathomable number of games that were released on the Commodore 64, Amiga, Atari ST, and most famously DOS that were made by one or two people, self-published, and have now completely fallen into obscurity to a point where it's not 100% clear who owns the copyright and who to give money even if you wanted to, which has led to the "probably-illegal-but-not-really-enforced" term of "Abandonware".
Mostly unrelated but if you are looking for this "effervescence" in modern times, don't hesitate to take a look at Pico8 games and Ich.io.
On Pico 8, everything is free (except the one time pico 8 licence).
On Itch.io I bought a ridiculous 400 games pack for a few dollars a few years back.
You have to dig a little but I found more gems in both those libraries than I expected.