Toxic masculinity is definitely not a part of relationships falling apart.

Anyone who had live through being in a group of single people through their youth and, as years pass, became the only one single on that group could probably confirm the experience. Friendships do not fall apart just because some male toxicity. It’s way simpler, it’s just that when two people do not have partners they can devote a lot of time and emotional energy to each other. When you are single a friend can easily be the most important person of your life. When you have a partner the amount of time and emotional energy that you have for friends is inferior, as you want to spend a great deal of that time and energy to your partner (as it’s natural). Then relationships became different. It’s not that it’s impossible to have “married friends”. But it’s certainly not the same as having a close single friend. And toxic masculinity does not take a part in any part of this process. The process is just a natural thing to happen on these situations.

Yes, people can cope trying to make new friendships. But that’s just a way to cope. Same as filing your live with hobbies and social activities can help coping with the lack of a romantic partner. But it does not solve the base issue. It’s like taking antidepressants for a depression, it helps, but it’s no solution, and the lack of antidepressants was not the issue.

Having a romantic relationship is important for many people. Denying that can be alienating, as you are denying personal experiences and personal feelings. I don’t think that solution is convincing people that their natural desires of being as loved as they see other people to be is just wrong and that they should live with even wanting that love (while they see plenty of other people enjoying that kind love).