Partner resentment after baby - how do we fix this?

I thought we were prepared. We read books, took a class, had conversations about split duties. But the reality is my wife is still carrying most of the mental load even though I'm doing more physical stuff. I handle night feeds, I do laundry, I take the baby so she can shower, but somehow she's still the one tracking doctor's appointments, ordering supplies, remembering when we're out of diapers, planning what the baby wears.

When I ask what to do next she gets frustrated that I'm not thinking ahead. When I plan things without asking she gets frustrated that I didn't consult her. I feel like I can't win.

Has anyone successfully split the mental load or does one person just naturally end up as the default parent?