My best friend is a (former) professional photographer, and we argue about it all the time. But we generally agree. DSLR, mirrorless, MF camera, etc. The quality, control, ergonomics and ability to use very specialized or unique lenses are significantly improved, and a phone camera is relatively awesome unless you factor in Advantage, Which in most situations makes it significantly more usable.
So it sounds like an 80/20 kind of thing.
80% of the time, a phone will give you passable pictures.
20% of the time, a pro-grade camera will give you amazing pictures.
Something like that.