Artists that use the same song structure...

I think it's fair to point out that "avant-garde" is hard to pin down when discussing music. Does Phillip Glass qualify? If so, he probably fits the OP's question reasonably well as much of his work follows pretty formal structural rules. Actually, while I don't profess much depth of knowledge of modern "avant-garde" composition, it kinda seems to me that a fair bit of it is formally pretty rigid, Schopenhauer is one that quickly comes to mind.

This isn't my listening hour "meat and potatoes", but I'll dip a toe in these waters from time to time.

"Phasecorrect, I agree--good is good and bad is bad, regardless of whether it's primitive, complicated or somewhere in between. Of course, it's subjective and there are no absolutes in this matter."

What a contradiction.

Tostadosunidos,

All bluegrass songs to me sound same regardless. I've been vendor selling records at bluegrass festivals and was able to sing one song during another song played on stage easily. Had lotsa fun making fun, otherwise would be definitely bored to death standing and listening to that squicky fiddle...

Mark Knophler "Nottinghillbillies" project with mix of classic country and bluegrass actually impressed me.

Another candidate of same song structure or would rather say same music structure is Phillip Glass. Most of his music based on typical minor arpeggios.

Anybody listen to avant-garde? Um, no. Pass.

Czarivey, trust me, it takes genuine talent to play bluegrass well. I don't care for most of the modern examples of it but I respect the musicianship.
You can also sing Folsom Prison over the changes to Pinball Wizard, and vice versa, but that doesn't diminish the value of either song IMO.
Not a fan of Phillip Glass, but at least he's repeating himself intentionally to achieve a certain effect.
Anyway on the bluegrass the new vocal people mostly don't ring my bell (I like Tim O'Brien) but the instrumentalists such as Sam Bush, Tony Rice and Jerry Douglass are phenomenal musicians. It takes real skill to do what they do. Try it some time.