It may never be proven but it's plausible that the JFK assassination was an inside job the same way that it's plausible that the Biden administration had the Nord Stream pipelines sabotaged.
Conspiracy Theories have varying degrees of plausibility. Each one should be considered on a case by case basis. Sometimes CT's are proven to be true. Examples:
- Watergate
- COINTELPRO
- MKULTRA
- The Pentagon Papers
- Iran Contra
All exposed by "the government" or by the media. In this case we're talking about planning the assassination of the president - in secret; everyone consulted went along - carrying it out - in secret, everyone went along - and then covering it up - in secret, everyone including people years/decades later, went along with the coverup. People decades later covered this up? Even today, right now?
Let's take the Nordstream bombing as an example. Imagine that over the next 50+ years the government and media conduct multiple investigations into the bombing. Democrats and Republicans in Congress, several generations of reporters in the media, historians and investigative journalists all investigating this.
Do you think the act would have been kept secret? Why would people in the Pentagon or CIA 50 years from now cover it up? For what purpose? For what benefit? There is none.
What you're claiming happen couldn't happen. Not covered up for half a century by multiple generations of Americans who have no interest in doing so. In fact, the benefit would be not to cover it up but expose it. Imagine the people in the CIA or Pentagon who revealed this? They'd be heroes, celebrated for their act.
If all you can see is "the government" and "the CIA" and "the media" and not see all sorts of people with all sorts of interests and backgrounds then I can understand why one would think "they" did this. But there is no "they", it's not a blob or single entity. It's all sorts of people with various interests. You cannot get generations of people - real human beings - to do what is proposed. Even worse for the proponents, there's no evidence for it.