The main problem with the phrase is how it limits the loneliness epidemic to men, though of course it's unsurprising in a patriarchal society that only men would be considered as the valid victims of a social epidemic.

But we need to be clear here. There is a loneliness epidemic. All genders are effected by it, furthermore the root of the problem is the extreme and increasing social alienation of late stage capitalism, and it's important that we keep that in mind. While you're not wrong that the type of people who tend to wail about the "male" loneliness epidemic are usually incel men who think they're entitled to a partner and blame "feminism" without even the slightest hint of self examination, loneliness in general is rarely if ever the sole fault of the individual, it is a social problem with social causes. So when you or anyone says:

You wanna know why you're lonely? Take a look at yourself. I can assure you, it has everything to do with YOU as a person

It is a terrible, cruel, and unhelpful thing to say to most genuinely lonely people and it is usually flat out wrong. This widespread immense loneliness has everything to do with a broken, communityless society, diseased by individualist ideology, borne out of capitalism and enforced by the bourgeois ruling class. Don't discredit the very real problem of widespread loneliness or throw the many lonely victims of it under the bus because a fascist minority has hijacked it and claimed to be the sole sufferers.