The Democratic People's Republic of Tankiejerk

Your example of a national equivalent of a "Prime Directive" ignores the difference between global politics and extraterrestrial development. Global politics based around isolation inevitably falls due to an inability to deal with some crisis that comes along. They will be a source of short term refugees and long term trade opportunities as whatever nation rebuilds seeks contact with its neighbors.

A population that has no chance of leaving the planet will have to deal with the crisis or perish. Star Trek never talks about the planets that they watch fall into chaos or extinction. It also shows the

Isolationist policies never work. It always turns inward and aggressive, like feudal Japan or post-Tito Albania. Or North Korea now. All other nations will have to deal with the remains of a fallen country so it makes sense to get ahead of the problem and inject some responsibility.