This is like saying Taylor Swift's grocery store deserves a cut of her royalties because she wouldn't be able to sing if she starved to death.

Song-writers get paid poorly because there is more supply of pop songs than demand for them. Taylor Swift's grocery store doesn't get a cut of her revenue because Taylor Swift could easily just switch to another grocery store. The same as she could easily switch to another song-writer (or write her own songs).

They do get a cut of her royalties, when she goes there to buy food. I’d question your assertion that one songwriter is just as good as another when we consider how many hits can be attributed to the same people if you actually check.

Actual success singers are your answer

No idea how that answers my question.

I mean shitty singers fucking rich

If “shitty singers fucking rich” it sounds like maybe songwriters do deserve a lot of the credit for hits!