…ppens to be a guy." Your description of six characteristics of the "nice guy" seems unlikely to me. The man who drops what he is doing to cater to his "friend," and often neglects other aspects of his life" is unlikely to be angry and resentful. It is probably true that he finds ways to insinuate that her current boyfriend doesn't do all that …
Thanks for the comment, Jeff. There's a big difference between "caretaking" and "caregiving." Someone who expects certain things in response to their giving is going to become angry and resentful if they don't get what they expect. That's caretaking. Caregiving is when we can selflessly give without expecting anything in return.
Guys who complain about being in the "friend zone" are usually also "nice" guys. it's fine to be friends with someone, but it's ALL about our intention. If our main intention is to "get" with someone and we can't turn that off to be a good friend, it'd be best that we set boundaries and stepped back.
This is something more common with women than men. I know too many stories of "nice" guys or "friend zoned" guys who were waiting around like creeps for a woman to become vulnerable so they could prey on her. No guy should want to be a predator.