I would be extremely surprised if it wasn't fixed by either
this or installing the ISRG root certificate.
It's not just PICO-8—most simple games that use OpenGL will work fine in Mavericks. Mavericks was the last time Apple updated OpenGL, which is to say it has the same OpenGL capabilities as even macOS Monterrey. This is quite bad for Monterrey, but good for us!
I've played Celeste, Dicey Dungeons, Baba is You... I'd say that anything 2D is more likely to work than not! Even for 3D, I've yet to come across a Unity game which doesn't at least start once I add my
dumb patch, although some do have graphical glitches.