When I was young I was fascinated by the story of the Endurance being trapped in the ice, not knowing if the ship would survive and I thought it was really mean of the captain to insist on maintaining normal work routines instead of letting everyone enjoy a nice holiday.
But it’s really important for mental health to keep good routines and some authority structures. Slipping standards of grooming and hygiene can be a sign of depression and some other mh disorders, but since lockdown and with wfh, it’s become apparent that many people don’t have to be actively depressed to struggle to maintain the standards.
I would check that there isn’t a serious underlying issue first. And I think it’s important to acknowledge that it’s not unusual. But it isn’t acceptable.
And look, op, even if you were the only woman in the world with this issue, it would still be a valid issue for you. Up to and including walking away.
He knows that if you left, and he wanted a new partner he’d be in that shower, smelling himself! It’s a non negotiable.
It’s not a completely straightforward problem to fix though. And there’s a lot of compassionate help available online (and even from professionals). It can be a difficulty for some people with adhd (because of the executive function challenge) or sensory processing disorders. That’s not to armchair diagnose him, but to point out that it’s a more common problem than you might think, with more than one cause and a plethora of solutions.