While stay at home mother makes some good points, especially because it is always valuable to see a counterparty perspective, "Here it is" is spot on. Wife makes a decision to be a stay at home? Of course it is referred to as the husband's mistake. Look, a spouse made a decision to be a stay at home mother, and it may not have been a very good one. But in the end it was her choice - and one that is not irreversible - she can get back into the labor market if she wants (and she will have to if she desires a divorce).
The bottom line to all of this is that men should put off getting married well into their 30's or even eschew marriage altogether. Marriage makes no sense for a man - the legal outcomes in divorce generally weigh in significant favor to women and most painful of all, all too often women use the kids as a lever when relationship issues arise. This is not a screed against women - there are plenty of men out there who cause all sorts of trouble and their partners have plenty of justification to complain. Rather, it is a comment that the rules of the marriage game make it painful for men and they often obtain what they want without the institution of marriage.
My own experience is disappointing. I come from poverty and horrible abuse and a broken family. No track scholarship - no education or anywhere near the life I have had. My wife comes from a upper middle class close knit family, ridiculously educated, and averse to athletics of all kinds. She is married to her family, and I am just the guy who keeps her in upper middle class status (I have made mid-six figures for 20 or so years). She is trained to get what she wants - which is a trait I admire - but the end result is a tepid relationship in which she has no respect for me. She controls access to my daughters - something she holds on to dearly and never will surrender - so of course I am a doormat because I absolutely want to support my daughters and give them everything I did not have. My daughters have had blessed and privileged lives, a tremendous accomplishment for me which transcends everything else. I understand my wife - her focus is on getting what she wants - and that is being married to her mother, sister, etc., and she doesn't need anything from me other than financial support and the social panache that comes with saying you are married. In the end it probably was not a good idea for her to be a stay at home mom for many years but it was clearly what she wanted. Moreover, she has a good second career in the public schools, so staying at home isn't at the core of the problem. My best course would have been to wait 15 years later before I even considered getting married - at a time when I would have had a better sense of self.
The OP has some of this in common. Scratch the surface and you will find her loyalty is to her children and family, and even when he had good times with his spouse he was likely 8th or 9th in terms of her priorities. The mistake was in marrying this - too late now but have to pick up the pieces and move on. She wants to leave because she has no respect for the OP.