I don't know, there's a trend of having men be punching bags, and your view of the film is fine, but it doesn't excuse her character or her behavior, imo.
I just think Mia is a horrible human being and the fact that people doesn't seem to think so, blows my mind.
The very first thing she does is flip off Sabastian...even though she knows she's wrong and should move out the way, while in traffic.
Then we see her with a rich boyfriend, and she just laves the table and embarrasses him in front of everyone to go see another guy
ALL that after Greg forgave her for forgetting about the dinner!!
So Mia and Sabastian date and he encourages her to write a play. Meanwhile, Sabastian had no interest in joining John Legend's band, but Mia suggested that he should, and when he heard Mia talking to her mother, he decided to sacrifice his artistic integrity for her, because he loved her so much. Up to that moment, that was his most valuable possession. Still, he did it for her.
So the band becomes successful and he actually begins to enjoy it and a new dream is emerging, but this new found happiness is in conflict with Mia, because she wanted the old Sabastian, so she uses that artistic integrity that Sabastian sacrificed for her....against him as a weapon to get him to leave the band!! He even invited her to go wit him on tour for a few days...but no, she didn't want to either, even though she had the time. She didn't want to support his success.
Anyway, her show failed and he didn't show up, and that was bad, so they break up....fine.
So Sabastian gets a call about Mia's audition and he could have easily ignored it, but no, he drives to her home town, fights with her to get Mia to go to the audition, she doesn't even invite him in to spend the night at her home...so who the hell knows where he spent the night? Then he comes back, picks her up and takes to the audition, sits with her and waits for her to come out of the audition, and he's so supportive that he tells her she's going to get the role, and finally takes her out for a nice walk.
She's like what's going to happen next and he's like, when you come back I'll be waiting.
Five years later, he still single so he hasn't really moved on and he's living the ORIGINAL dream that Mia insisted that he wanted ignoring the fact that maybe his dream had evolved into something bigger. So he's living a life by himself that she sort forced him to have.
Meanwhile, Mia is a movie star and married to a guy who is very similar to her original boyfriend, Greg. So Mia and her husband go to a show and while in TRAFFIC, Mia says, "I do not miss traffic in L.A.", so no musical dancing from the beginning of the film...basically saying, that's how people feel when they're unemployed but once they make it, they really look down on it.
She then says, let's skip my friend's show...let's go to dinner instead, but wasn't she very upset when someone didn't go to HER show? Right, she broke up with Sabastian over that. She's exactly what she said it was so horrible and here she is, basically doing the very same thing.
Then, when Mia and her Husband go to the club, she realizes that this is Sabastian's place, and knowing this does she take a seat on the back? No, she insists on sitting right in front so when he comes out on stage he'll see her. That is just savage. She could have sat on the back and THEN said hi after the show.
So Sabastian manages to keep his composure and he plays the very first song he played because he remembers it from when he saw her at that Italian restaurant. Now, you said that he imagines his life with her, but I think it was Mia imagining her life with him because it was done from her perspective. And there are 3 moments, he kisses her because he's the "ideal boyfriend " and never takes the band job, then a shot of her play with Sabastian watching, and finally Mia and Sabastian sitting in the club married with a child, so ultimately MIA has EVERYTHING she wanted, and HER ideal dreams but it completely neglects his dreams.
And in the last scene, they both look at each other, and yes...he totally lets her of the hook...and she knows it. She's like thanks for not letting me know how horrible I am. She's one of the most horrible characters I've ever seen in a film to be honest. She's living her dream, and he's a ghost of her past, living an old dream, alone and thinking about Mia because he's still in love with her, but she doesn't have to feel guilty about it.