Dear God, I hate! hate hate hate the Prime Directive!!!
Within the Trek Universe, it was an excuse to not get involved with any races if it meant you had to deploy resources to provide something for that race. Even in cases where they were involved by accident, they still call upon the mighty Prime Directive, even when it doesn't matter anymore.
For example, the TNG episode "Who watches the watchers" They reveal themselves to a primitive race by accident. They have no choice to explain to the indigenous people there who and what they actually are, otherwise they would have fucked things up pretty badly for them. Yet at the end of the episode it was basically "ok, you know what we are and where we're from, but we still won't get involved with you, you are on your own to reach our level"
The right thing to do was say "Ok, you know who and what we are, so now we have a moral obligation to at least send some Starfleet personnel to guide you on all the modern science we have, and to help you develop the technologies on your planet". This way, they would have probably been ready to join the Federation in a few decades.
But nope they don't do that. On Enterprise, they did even worse. in "The Communicator" they left an alien faction scared shitless that the other alien faction whom they are at war with has: Cloaking technology. Directed energy guns. Genetic engineering. Antigravity flying vehicles. Imagine the kind of repercussions that will have. It was easier to just tell them the truth. They already believed in it before they were misled.
Yet in TOS' "A piece of the action" they had no qualms about leaving the communicator on the planet, and it was left as a little "joke" to end the episode on a lighthearted tone.
And in Dear Doctor, they had no problem providing a workaround (already interfering with "natural evolution") but refuse to provide the cure due to fear of "interfering" with natural evolution.
Outside of the Trek universe, it was clear the "Prime Directive" was simply there to save money, since the Federation never had to get involved in anything, the shows never had to spend the money to show something that onscreen they could avoid doing. All basically a copout to be fucking cheap fuckers.