DH is the same and I'n basically a solo parent or lone parent while being married. I'm almost certain he has ASD & ADD (I also have ADD) which means many of his behaviours are not malicious or inherent selfish. If he's tired then he needs to sleep or retreat somewhere, and he can't deal with the overstimulation of DD or noises of children's shows. He "stims" with his phone by scrolling through endless chats and repeatedly checking email, online banking etc. He's not very good taking care of himself either, left to his own devices he will often not eat the entire day and then get takeout/gorge on crisps so expecting him to meal plan and feed a toddler is pointless.
Sadly there's no easy answer except that 2.5 is a very difficult age and you've also had the cumulative exhaustion of taking care of a baby during a pandemic. I was close to breaking point at 3 when DD stopped napping during the days, not in nursery and I had to do every single mealtime, waking, naptime, evening routine plus all the entertainment and trips in between. DH has never been with her alone for more than 5 hours since birth and has never taken her on a day out alone (exceptions being a trip organised by his mum and he tags along). This sounds pretty terrible in writing by DH is actually successful in his career and always well groomed, but really lacks day-to-day executive functioning skills.
It's easy to bash "man children" but I guess this post is just to say that some of those men may not be fully NT. All the SEN children that are mentioned across MN do eventually grow up and become adults with more or less functioning lives. The ones on the less severe end of the spectrum can have perfectly "normal" lives from the outside but often at the cost of a partner who picks up the slack. Both of us work so finance isn't an issue and things are split evenly. (I wfh after DD is asleep so that's also part of the exhaustion because I have no downtime. My "treat" is to be able to work).
OP, it does get marginally easier the more independent your child becomes. I've firmly drawn the line on not having many more children and once DD is in kindergarten/school then I feel I can cope with it even if DH doesn't contribute. It's the constant toddler fights, tantrums, finding things to do to pass time in the time of covid, having to dress them/undress them, change diapers, wipe bums etc that's grinding me down. The thought of being a solo parent to an older child doesn't bother me much.