Care for your own social life and you won’t be lonely. It is not only romantic/sexual relationships that fulfills that need.

Completely untrue for the majority of people. It's only a small subsect of ace people who have no need for romantic relationships. The vast majority people need them in order to feel fulfilled.

And the problem is that, statistically, many men will be lonely.

I am also interested in what you are proposing in practicality to happen?

I'm not sure about a solution...aside from entitled, getting women to date men they're not attracted to is simply practically impossible. As a band-aid though, and maybe a step towards a true solution, I think we as a society should be able to acknowledge that this is a societal problem and have some level of respect and support for the men it affects. Not just "get better and women will like you lol loser". Not get immediately screamed at for being an incel just because you bring it up.

Did you know that the most lonely group are older women? Especially when it comes to relationships. Do you see them whine and demand men to go on dates with them?

All the time, actually. I am friends with a group of single women in their 50s and 60s and they do complain about this exact issue all the time. Except no men can meet their standards, which circles us back to the original point.