That seems like an absurdly stupid take. Shared interests mean there is benefit to grouping up and trying to affect the world around you as a collective. This can mean something small like making a friend group out of like-minded individuals, or something big like trying to unite at the societal level and affect politics. "Just a state of being" applies to almost everything. No brotherhood doesn't follow from that.
The lack of comradery between men in general and incels in particular has more to do with how even men don't innately care about other men and their misery. We evolved to compete to the death over resources / access to women. Puts a pretty strict limit on how much unconditional empathy we could develope for other members of our own sex.
Also, sites like this filter for exceptionally disagreeable people (while more agreeable people land on reddit as male feminists or just go through life while keeping their mouth shut and their head down, even if they share some of our resentment deep down). Putting a bunch of hyper-disagreeable people in one space is bound to produce lots of infighting and little cooperation.
Then there is the constant feminist brainwashing everyone in the west goes through since earliest childhood through all aspects of culture.
And last but not least, dating apps are like slightly more than 10 years old, the situation hasn't been bad enough for long enough for a real counter-movement to gain traction. This could easily change once this current generation of men reaches adulthood and the former generations are pushed out. Although any change that results from that will come much too late for all of us.
Societal norms have been changing rapidly for the last few centuries. It seems silly to think "things will always be like this" when you live in a time where some people at the top decided to make transsexuality socially acceptable (or more like untouchable) and did so with such ease and such speed. Being overly pessimistic is no more rational then being overly optimistic. The indifference of the universe goes both ways.