The biggest moat is capital.
PE is buying up things like medical practices, law firms, vets, etc, where typically there would be an upwards path for one generation to hire new blood to cover their markets and then sell partnership stakes to them when they want to retire. But why should an owner of a practice sell to their junior staff when PE is there offering 2, 3, 5x as much?
Consolidation of these kinds of businesses at the hands of PE is endemic of systemic lack of capital acquisition of a generation of people, held down by debt and concerns about practical shit like healthcare.
PE is just a symptom of larger macro economic trends, namely the depletion of the next generation from free cash they could use to become business owners.