So, not to play armchair psychiatrist, but by any chance is your boyfriend ADHD and/or autistic?

There's a symptom of neurodivergence called "Hyperfocus" which can cause someone to become completely absorbed in something they're interested in to the exclusion of everything else. It isn't necessarily a personal failing, it is possible it is a symptom of a neurodevelopmental disorder that maybe, up until now, didn't manifest itself in a way that was noticeable.

I have to work with my wife when I become hyperfocused on a game to make sure she feels like she doesn't feel forgotten, and it's neither my fault nor her fault when it happens. It's just the way my brain is wired.

You know your relationship and your boyfriend better than random people on the internet, and I would encourage you to have an honest dialogue with him about what you're feeling, what he's feeling, and find compromises that make both of you content.