Money.
It comes down to money for materials, sheet music, hymnals, and instruments.
Places with bad music have volunteers that can carry a tune. That seems to be the only criteria in some places.

I know. I’ve been a professional church musician since right out of college.
Bad chant is worse than no chant.
I agree that hymns that are clearly meant as solos have no place in the liturgy for the people. If they have taken a traditional hymn and switched it up with many key changes, no one is going to like it or sing it.
They are called choirs for a reason. They are supposed to lead the faithful as one voice. Not flex their vocal chords unless it’s something proscribed ( or requested by the Pastor) and very difficult.
Also many people just don’t like chant (honest, I am not kidding) including pastors.
They want what will appeal to many and get the job done. The job interview before this current one, I told them I was well qualified to teach chant, and would be willing to have one Mass Schola dedicated to such. The pastor and the entire group of cantors were horrified at the prospect. No kidding.

They passed me over for a convert who could sing very high. Nice woman, but she had no clue what to use at Mass and with no mentoring. They sing the Allelluia before and AFTER the Gospel.
Sigh. Another “innovation”.
I was the Music Director at a parish for 16 years and started at 6 grand a year, sixteen years later…making 11 grand. And I did EVERYTHING.
Bought music, trained people, rehearsed with people, made programs, printed stapled and folded the programs (For FHC, CONFIRMATION, FUNERALS, Christmas and such) and played most funerals for free because everyone thinks the funeral home or the priest pays the musician. THEY DO NOT. I would have to take a personal day from my real job with no pay, to make a funeral nice for someone. I did it because it’s the right thing to do.
But a gurl’s gotta eat.
Just sayin’