I think that notion that "sex sells" is partial because that's what people say nowadays and those people who write those Smut stories don't steer anywhere near being nominated or winning elite awards. Forget about online platforms like tapas and webtoon. Focus on the comic artists that you consider icons. What do they produce? It will answer your question about the notion that "sex sells".
Secondly, not to hurt your ego but I have read comics with much better skills than yours. Sometimes, it's better to be frank with yourself because the artists you are looking at must have had more trainings, practice, success, failures than you have experienced, so it's NEVER wise to compare your skills to anyone. You do not know where they have been or what they have learned during their years of drawing.