How many times have Kirk and Picard broken the PD and have never be punished for it? I consider it more of a suggestion than an absolute law.
Than how come other Starfleet characters treat it like it's an absolute? When Janeway and Paris travelled back in time on a planet that was about to be completely destroyed with it's entire population, Tom has the idea of warning them which leads to this exchange.
JANEWAY: Don't even think about it, Tom. The Prime Directive is clear. We cannot allow our presence to alter this planet's natural course of events.
PARIS: Even if the natural course of events is annihilation?
PARIS: My father used to talk at length to us about the Prime Directive, once a year, like a holiday sermon.
JANEWAY: He considered it the guiding principle of space exploration.
PARIS: To be honest, I tuned out most of his sermons years ago.
JANEWAY: Well, tune back into this one, because I agree with him. You have no idea what the consequences might be once you involve yourself.
PARIS: The consequences would have to be better than mass destruction.
JANEWAY: You're not to warn these people. That's an order.
Janeway's stance on the Prime Directive certainly doesn't treat it like a "suggestion". She tells Paris that he doesn't know what the consequences would be if they got involved, and he refutes it by stating that if they do nothing, the entire planet (including themselves) would be destroyed. Instead of actually contemplating that notion, she instead enforcers her stance by just pulling rank. She doesn't use reason, she uses rank.