that isn't true except for weirdos locked in rooms all the time. Plenty of good comic art around, there just needs to be more refinement of the craft, more coherent series, more recovery from the days when there were parasites demanding for their lacks of personalities to be features in comics, etc.
mangaka like the second guy who does one punch man spend their whole life basically in a trance honing their craft to perfection, while americans (who are sociable and have to interact with people from much more varied backgrounds) can't maintain that kind of a trance
so, guys like me try to improve the quality of artistic teaching, and also brainwash the peasants like some dark japanese cartoon character. what can i say. it's the nuke lineage