Most of the criticism of it I've seen is about how the concept's been warped to mean women aren't putting out enough for specific men. Other people will also point out that modern society is isolating in general. People who aren't men who are experiencing loneliness might have some skepticism about the idea it's a man specific issue.

There's also some wariness because topics about issues men face can translate for some men into a violent rage towards women. As seen with the involuntarily celibate movement.

People of all types can take genuine grievances and find a target to take it out on. Like income inequality translating to hatred of immigrants. And violence towards them. When you're the mistaken target of those grievances, it can be simplest to want to get away from the conversation unless the person starting it is clear they aren't targeting you.

Those are my guesses as to why people are skeptical.

https://www.npr.org/transcripts/1263527043 Some discussion in here about the topic, but also criticisms of the topic.

https://trinitonian.com/2025/02/14/unpacking-the-myth-of-the-male-loneliness-epidemic/ This opinion article criticizes how influencers drive the conversation, to its detriment.

https://www.fridaythings.com/recent-posts/male-lonliness-crisis-incel-men-friendship-mental-health This person brings up the idea that women are wary of the idea because it seems like they'll be expected to individually solve it regardless of their own wants and needs.