Your post really resonated with me. Like you, my kids are 19 months apart. They are both graduated now, but the initial separation was difficult for them to navigate. Some women are just not naturally maternal, just like some men are not naturally paternal. Mine was and is nott mother material. Now, I cannot speak to your situation, so I'll relate mine and hope at least something helps.
My EXWW came from a very dysfunctional home, with a surly, abusive father who really screwed up her view of me, and a passive mother who screwed up her view of women. Together, they screwed up her view of relationships. Lucky me. Thus, proper, healthy modeling was never a thing for her.
Her A was rooted in a need to be "happy" and "self actualized"... the usual bullshit. She could have used a good dose of Seneca.
Anyway,fast forward to S/D. The kids had two homes and alternated weekly. Her home was chaotic and spacious. Dinner was seldom made and the fridge often empty. The girls had to fend for themselves, often asking me for leftovers for the first night with their mom.
Comparatively, every Sunday when I picked them up, I made sure I had a comfort meal in the oven, waiting for their arrival. I wanted them to associate coming to dad's house with good, positive memories. We would even play a game where I would pick them up and they would be starved, asking if I made anything. I would act confused and forgetful, feigning incompetence. Then, when the entered, they would get hit with the smell of a family dinner. In five-years,I failed only twice.
If I am being honest, there was a small part of me that wanted to show them and to some degree their mother, that I was not only the better parent, but just how much she lost. But there was a much bigger part that wanted to preserve their childhoods. I felt like I had failed as a husband and father, and I wanted to mitigate the damage I caused I choosing to leave their mother.
I am a deeply damaged and flawed man. I used to be so many things before the A, and it seems those things are lost. But, despite everything, I've tried to rebuild with the tools I've been given. My girls miss the old me, at least they have said as much, but he is dead. The new me, a little battered and bruised, keeps moving forward, undefeated. What is interesting, is that both girls have chosen to live with me after graduation, so I take that as a win. It's funny. When I tell people, usually women, I get an "Oh, really..." then they usually say something bland and move on.
You can't control your EXWW and how she parents. And unless it harms the kids, it's just something you will have to navigate and endure
As infuriating as that is. What you can control is how you parent, the home you create for them. Make itthe best you can. They will take it for granted when they're with you and miss it when they see not. You could not ask for more. And, as they get older, they may gravitate towards you more, just as mine did. Hopefully, they will have a good relationship with their mother, but that is on her, not you.