Yeah, I'm leaning towards that conclusion as well. While I don't publish my writings, I have a few friends who do. The stuff that comes from Lulu, even the cheapest "models", is honestly fine. The ones from Amazon, not so much.
Of course if you typeset and edit your book like a moron, that's going to impact the quality, but this has nothing to do with POD.
I have to recommend the following:
https://press.uchicago.edu/ucp/books/book/chicago/D/bo213648...
Fewer and fewer books get this treatment by experienced professionals and it is often left to the author to do this work. This is really a great resource!