I feel this is a strong theme, MC is being blamed for not being a 'good victim' (cit.).
I said it before, the whole thing reads like MC is not entitled to his feelings and this is suggested since act 1 when Lacey states that there should be a limit on his punishment of her.
L "Maybe if this were only about the past, then maybe I'd feel a little differently."
L "I'd still understand, but I might feel like we should set a time limit for how long you punish me."
This is her policing what MC should feel, YOU fucked up, don't want to face the music? Walk away.
Well, shall we look it at another way? Does Lacey has the right to be angry at her parents forever or until she feels like it? Her mother seemed eager to talk with her so you can say that her cutting her off is akin to punishment? Is she entitled to do so forever? Shall we set a time limit? We are talking about the past anyway.
I want to see how many would argue that she doesn't have the right to her feelings, she is a victim and she is entitled to a lot.
MC has been abused and betrayed by Lacey, and we are not talking only about the past (where she was fully aware of it), she keeps on doing it right now.
If any of you remember the dialogue about the JD, and how much Lacey spoke of boundaries and how much she is aware of MC limits (another of those calrity moments where Lacey is a relationship guru), add what is added then by Dianne in act 2 and how she breaks them and then blame MC for it "because he did not stop her".
And yet in act 3 this is exactly what is being told and underlined, MC is the one not putting the right boundaries, MC is the one that "holds things over her head", MC is the bad guy.
At least in act 1 and 2 MC was assured by most of the cast that he is not a bad person, in act 3 not so much.
No one is owed forgiveness, the victim can decide whether forgiveness is granted on their own terms.
And even then forgiveness might not even be on the plate at all, maybe acceptance is the only thing on the plate, and the victim is the only one that can decide that.
Remember Anna dialogue after she catches Lacey with Isaac? (I
wonder what would have happened if Isaac begged for sex again? 
)
Lacey is held accountable by her (briefly) and it is made clear how Lacey spins the truth to appear as the victim, to excuse her behaviour and shift blame.
It was a nice clarity moment, and yet it has been forgotten completely.
I won't advocate for a specific healing path, everyone is different, but one thing I am sure about, MC needs to heal for himself, not for Lacey, not for the "friends" or anyone else but for himself.
Strangely enough it is what MC hopes for Lacey, that she heals for herself, not for the benefit of others, not even his own.
MC is not granted this privilege, he needs to heal because he affects others or because his issues have a bad influence on Lacey mental health.
This is obviously a slip up, because the author cares less about him, at least in act 1 we had some moments that blamed Lacey for hurting him (Anna scene at the club), now even Anna has done a full 180 and blames him for being angry for
being cheated on because "Lacey was playing by the rules", which is absolutely bonkers, morally corrupt and is filled with victim blaming.
Which is?
The threesome was a very problematic scene for many reasons (yet I am happy that I got the participants right in my prediction), as again it breaks what we know about her.
So her being shared stopped being a sign that MC didn't care about her and is just a minor thing, while it was one of the bedrocks of their relationship, a cornerstone of her personality.
It was obviously added for the sake of it, there was no buildup to it and it is treated by Lacey without a care in the world, yet when the topic was breached in the past aftercare between them was mentioned.
MC has a choice to go with it or not, but where are his feelings about it? Even in a healthy relationship a partner that is offered something like this point blank might be hesitant and would feel something is wrong.
Even if he says no, wouldn't MC be suspicious? Wouldn't he be jealous and think that Lacey wants to be with Lorenzo? (at least this is how I would see MC act compared to his past behaviour).
I think the prof started to care less and less about writing MC feelings he wanted this scene, so the characters had to bend for the sake of it.
The possibilities were endless, look at how MC tries to help even his worst enemy Isaac, Lorenzo could have pleaded to him and Lacey (or to Lacey to then plead with MC) have some emotions and some willingness to help stem from MC seeing how Lorenzo is damaged.
I think a lot of folks got their hopes up with the title of the act "learning to let go" and came at the conclusion that Lacey was the source of pain so MC could have let her go temporarily so he could put a few step forward on learning to be self reliant.
Frankly, it would have been way better compared to what we got, there was a high possibility of drama and deep emotions to come out from both Lacey and MC.
A lot of learning could have happened for both of them and they would have grown together (separated but together, I hope you get what I mean).
I cannot stress enough on how act 3 falls flat, with the dumpster fire that is Vegas to the abusive behaviour of MC "friends" (looking at you Anna, Jeanette and Veronica).