Obviously looks come first, and part of that is based on a person’s visual preference.
But let’s say an average looking person and they have a decent personality, that will just make them get friends but not establish a deeper connection. They need to be more daring and open up (hobbies, passions, lust, etc) and if the two people click then it’s easy to form a relationship.
Incels think there’s a formula and they try different strategies which obviously don’t work, then get pissed off. Like incel stalker Josh who thinks following Nayeon on airplanes will get her to love him. You also need to be realistic, no celebrity will go for a random incel. If they were actually very good looking like a male model then they wouldn’t be an incel.