@ruin no developer of anything approaching the broad usage patterns of a browser can EVER test everything.
I didn’t have devices / time is NO excuse. You do your best. You reach out for help where needed.
For context i have almost 30yrs of coding for a living. Avoidind & removing accessibility because you’re a small team says that disabled people aren’t valued equally to non-disabled people.
You prioritize that work over the next whiz-bang feature that isntrely needed. It’s not hard.