My house entire attic has plywood flooring over the joists/insulation.

It is nailed in and a pain in the ass to remove.

What is the best way to add additional insulation to the attic? I worry the plywood/insulation underneath has a bad r value.

Do I need to take up all the plywood and re insulate the batts? Should I just loose fill on top of the plywood?

Ideally I want to air seal it to but taking the plywood up will be a nightmare.