That's a hugely subjective comment and there are plenty of instances throughout history of a powerful CLI and sophisticated GUI being included as part of the same OS (Xerox Alto, BeOS, NeXT, Plan 9). Linux and *BSD's have plenty of popular WM / DEs too: personally I'd rate KDE above anything commercial I've used but that's my subjective preference. Heck these days even Windows can be argued as having a "powerful CLI" with both WSL and Powershell existing, and the Windows UI has it's fair share of fans (regardless of what our own personal preferences might be).