I agree with most of this (though "Toxic Masculinity", like "Triggers," "Privilege," and so many others, is a phrase that used to be useful and has now been utterly destroyed by the socially fashionable).
The general "response" to the incel phenomenon seems to be to diagnose (and dismiss) them as the sexual version of anorexics: people who have an unrealistically negative view of their sexual appeal and potential and end up harming themselves as a result. If they could just stop being so hard on themselves and relax, they'd be fine!
This is a problem for two reasons. First, a lot of people genuinely are seriously, perhaps even hopelessly impaired in terms of finding a sexual partner. Appearance, money, and the ability to navigate a host of social and psychological interactions are vital to the process, and some people lack enough of these that their ability to find a partner is slim to none, and will not be improved by a few personal tweaks. The situation is similar to depression: everyone has felt down at some point and gotten over it with simple coping strategies, so they inevitably suggest these strategies to depressed people, not realizing they're dealing with a much deeper problem.
But second, the real issue, as demonstrated in the discussion here, is that a large portion of the population has an unhealthy obsession with having a sexual partner. They view it both as an unqualified good and as a necessity, and are thus terrified of going without it for any significant period of time. For these people, you are not complete as a person unless you're in a relationship. This is a profoundly unhealthy and destructive way to live life, even for ordinary people.
Relationships CAN be good. They can also be bad. On the whole, they generally end up creating almost as many problems as they solve (and sometimes more!). Having a partner is optional. It isn't like air or water or good nutrition. You have to find peace within yourself, with yourself, before anything else. Trying to fix that with any outside thing, including sexual or romantic partners, is a recipe for disaster.
This thread is full of people continuing this warped line of thinking. Relationships aren't evil, they can be good and they can have positive effects on people. But they aren't necessary, and they won't fix you. Only you can fix you.
In short, our culture very clearly has an addiction to sex and romance. Not in the dopamine sense, but because we believe the answer to our problems lies in someone else. In people with the ability to feed this addiction you get mild to moderate problems. In people without that ability, you get incels. Incels are just the most extreme symptom of a deeper disease.