Everyone’s idea of physical attraction will be different. There’s also people who don’t strongly have opinions about physical attraction as they do about personality attraction. And then you have intellectual attraction.
There are people out there single and happy regardless of their attractiveness and not even bothered with it. They aren’t even lonely. There are people where it’s not even their lifestyle. There are plenty of people who may not appear physically attractive to one person but are in happy relationships. So physical attraction is a red herring argument when it comes to describing what makes a person turn into an incel.
It’s about how an incel handles rejection and being alone. There’s much more to do with obsessiveness, loneliness, entitlement, anger transference and toxic thinking than it does with attraction in and of itself. The toxicity becomes more a self fulfilling prophecy.