The author mentions GEOS among those efforts that, and I quote:

> [...] had good intentions but pushed the machine in ways it wasn't designed for, compromising on speed and usability in the pursuit of features available on more powerful computers.

I must be honest and say the statement feels a bit puzzling, since C64OS certainly wasn't something the C64 was designed for...

Maybe they are alluding to the fact that GEOS was using graphics mode for the GUI (which makes drawing the UI slower and requires more memory, thus arguably would require a more powerful machine) where C64OS is using text mode (plus the graphics split mode) which arguably is more suited to the C64.

I remember switching floppy discs rather a lot when trying to use GEOS back in the '80s.

My C64 now has a USB interface 8)

Same. GEOS was really cool, I was blown away by the 80 column mode. But it felt more like a gimmick and I never ended up really using it for anything real. But then again, I was 10 years old and more interested in playing Raid on Bungeling Bay.