> I'm wondering if humans are mostly incapable of producing great things without (artifical) restrictions.
Here is an opinion to support your hypothesis from a couple of different domains: poetry and music.
While some people prefer free verse and avante-garde music, what stays most in my mind, and what seems to endure longest overall, are poetry with regular rhyme and meter and music that follows standard patterns of melody, rhythm, and harmony. Having to force their creativity into those sometimes rigid frameworks seems to enable many artists to produce better works.
Maybe a counterexample to it, not sure if it can be applied:
I write software in ABAP, which is a weird and ridiculously complicated language that has inline SQL and type checking against the database and has never had a major version that breaks old stuff, so code from 30 years ago will (and does) still run.
I used to have fun working around the quirks of it and finding solutions that work within the limitations, but now I'm just frustrated by having to solve problems that haven't been around for the past 15 years in the rest of world and looking at terrible code that can't be made any nicer because of those limitations or because customers don't give a shit as long as it works most of the time.
Here is an opinion to support your hypothesis from a couple of different domains: poetry and music.
While some people prefer free verse and avante-garde music, what stays most in my mind, and what seems to endure longest overall, are poetry with regular rhyme and meter and music that follows standard patterns of melody, rhythm, and harmony. Having to force their creativity into those sometimes rigid frameworks seems to enable many artists to produce better works.