No, it's not a delusion, it comes down to a few simple things like sensor size.
I have an entry level Canon DSLR from 2007, 7MP, which takes far better photos than any smartphone I've ever used.
The reason is pretty simple, it has a 1 inch square area for its sensor, while the smartphone sensor is about the size of a small pinky nail (1cm squared or less?)
For any given period of time, the larger sensor can capture more light at once, either taking better exposed or faster shots, and having far more data in which to encode a digital images pixels.
It's certainly insanely impressive what modern hardware and software get out tiny sensors, but bigger sensors are still incomparably better -- AND can benefit from many of the same advances small sensors use.
It's kind of like car engines. It's always impressive when someone gets insane performance out of a tiny engine, but no one disputes that a big engine is going to be more powerful than a small one, especially when displacement is the only difference.