The environment can be larger than whatever system you drew a notional boundary around and still smaller than the universe, so not being able to reverse the universe isn’t a problem. Here, I’ll make it explicit: imagine it turns out that your “environment” is actually a Laplacian monstrosity! You’re just a subsystem. All concerns about irreversibility are thenceforth questionable.
The environment can be larger than whatever system you drew a notional boundary around and still smaller than the universe, so not being able to reverse the universe isn’t a problem. Here, I’ll make it explicit: imagine it turns out that your “environment” is actually a Laplacian monstrosity! You’re just a subsystem. All concerns about irreversibility are thenceforth questionable.