There are also people who do both. I started out with JavaScript and PHP and do a lot of React/Angular/Laravel stuff. But I have also worked on complex performance-sensitive business systems written in a mixture of C++ and Rust.

My boss at my last job had done the opposite. Coming from a tradtional compsci C/C++ background (many moons ago), he learnt Angular 2 for a frontend project that required it. Both his C++ and frontend code were among the best at our company.

Saying there aren't good fullstack engineers is like saying multi-instrumentalists aren't good musicians. Sure, the very very best violinists probably don't play other instruments at a high level. But the average multi-instrumentalist (who plays the violin) is a lot better than the average violinist.

That attitude, as if there's no such thing as a complex system on the frontend, is a pox on the industry.

Building complex systems is far from limited to the backend.

Correct. There is a difference. Typically these 2 "types" sell themselves very differently also.

What actually is your point? Reading between the lines, it seems to be:

"Anyone who calls themselves a full-stack developer is garbage - it's just a matter of what side your garbage is on."