"Unchallenging" isn't quite right for the food comparison, you're correct.
For instance I don't consider The Beatles, say, or Michael Jackson or Jay-Z or Frank Sinatra or Mozart necessarily "challenging" (for some people some of those artists are), but would consider them "healthy".
Healthy food can be tasty and delicious, too ; ).
I do think if someone listens only to music without any depth (again, I'm using the Beatles - or Led Zeppelin, or Jimi Hendrix, or Taylor Swift, or Robyn or Daft Punk, or Lauryn Hill, or Billie Holiday, or Kanye West as examples of popular artists with depth), it is a lost opportunity for development of the self, and in a sense, "stunts" the growth of one's own self.
It's also just a huge loss. There's so much beautiful art that is not "challenging", and much of the "challenging" work simply requires a friendly environment and an introduction, and they yield huge rewards.
At the same time I think the emotions which a lot of art can stimulate cause fear to a lot of people, which can be cause for avoidance of them, but that's a separate (albeit related) conversation : ).
I dunno. I did start off talking about "challenging" art. But, the line is so thin!
I don't think Miles Davis' "Kind of Blue" would "challenge" many people - it's maybe the most popular jazz album, one of the best, and a beautiful piece of listening. It has lots of depth though, and his other work can be considered challenging, for sure ...
Really I guess I'm making an argument for the value of cultivation of the self through education, which includes the arts : ).
There's just so much out there: Indian classical music, Afrobeat, Latin jazz, country music, tons of electronic music from everywhere, traditional Chinese music, etc.
Not unlike programming/computer science, there's so much neat stuff that people have done in the arts that often people don't even realize exists.
Not all of us have the time and the inclination to do the deep digging, but, I think it's important to have a balance and at least an appreciation for the vastness of what exists in our lives, and that doing so enriches our selves.