Whilst we are all playing with the concept of Irina as not a great mother, I's like to put in my 2 cents and project for a moment. In the show it is really obvious how different Ilya and Alexei look compared to each other, and I just so think that Alexei's resemblance to Grigori made her resentful of him, I think to her he was more Grigori's son than hers. With her depression as well, she looked at him and just saw the man who was keeping her trapped in this life that she hated. Then Ilya comes along, and he looks just like her, that's her baby and not Grigori's. she projects her feelings onto Ilya, it becomes them against Grigori and Alexei, she tells him things about their marriage and her feelings that he's really not old enough to understand and shouldn't be forced to listen to anyway, but he feels so isolated from his brother that he internalises it as Irina being a perfect martyr who is protecting him from his dad and brother. Yes, his father is an abusive asshole, but I can't see that teenage Alexei is a total monster either, he likely wanted his mother just as much as Ilya but wasn't given the same level of affection or attention and saw Irina as cold and harsh. This probably pushed him to fawn as it were for his father because he just wasn't getting the attention from her, yes Grigori was still an asshole to him, but it was more than the disinterest he got from Irina. It's not really her fault because she was in an impossible situation but I know in my bones that Alexei felt abandoned by her. She probably stood up for Ilya more than Alexei too, Ilya got to play hockey his whole childhood and that is not cheap. In the show we see Alexei in a not great apartment and working in the police. Part of it is his own actions but Ilya probably got more resources than him because Irina would actually stick up for him and Grigori saw potential in Ilya.
Not to mention, I think Irina was the ultimate boy mom about Ilya, in her depression and that he was in her eyes the one good thing in her life, and I do think she projected her own feelings onto him. Not in an incest-y way at all, but he was her "little man" and she was possessive over him. I don't think she liked it when Ilya talked about liking girls at school, because he was hers and not old enough for any of that yet. He probably became her caretaker when she was in the midst of her depressive episodes, like fetching her water and food and trying to convince her to get up and shower or lying down with her when that doesn't work. Alexei probably watched all this, and saw Ilya missing school when she was really bad and it made him resent her more, because how is it that he is getting almost no attention from her and she is smothering Ilya to the point of it being detrimental to him.
Controversially I do think it was selfish of her to commit suicide in a way that almost guarenteed one of her children would find her, depression and suicidal thoughts are hard to deal with, but she left Ilya with memories of one of the most traumatic things a child could experience when she had other options. I also agree when other people say that she was probably a very conservative woman who would not have approved of Ilya's bisexuality, and especially not Shane. I think it boils down to the fact that Ilya was so manipulated by her and the people around him, with her pitting him against Alexei especially that he has put her on this pedestal in his head because if he doesn't then he has to actually examine what his childhood was like and see her as a real woman with real flaws when she is the one tangible thing he has to hold on to from his childhood as "good".
I aware this is word vomit but I really think their is more to Ilya's relationship with Alexei than the show or book dives into. No one is born an asshole and Alexei definitely had just as shitty a childhood is Ilya's. And you bet your ass Ilya gets almost agressively defensive over the memory of her if anyone around him questions her actions. In my personal opinion the biggest fight, that almost ends their relationship between Shane and Ilya is when Shane questions whether Irina was fair to Ilya and expresses sympathy for Alexei and Grigori about her suicide. Ilya just point blank refuses to see Shane's point, and accuses him of siding with his brother and father. Idk people, just give me toxic boy mom co-dependant with her 12 year old, conservative and emotionally manipulative Irina who was a real and complex person but in the end just as detrimental to Ilya's mental health as his father.
I did not proof read this, please understand my vibe and intentions via telepathy. It was however lovingly handcrafted for the enlighted few with shocking mommy issues.