However, I'm also aware of four simple facts.
First, it is possible that Oswald acted alone. I don't think it's likely, particularly when he gets knocked off by a guy that runs a topless bar and has known mob connections. I have several other problems with this scenario, but the Ruby hit on Oswald is the biggest indicator to me that something bigger was going on.
Second, LBJ, even in his biography, was more interested in getting the Kennedy assassination investigation finished than in an actual investigation (in his book, he phrases it more like putting the American people's mind at ease or something. It's been years since I read it).
Third, so many people have traipsed over the evidence that it's impossible to clearly determine what is fact, wishful thinking, planted evidence, lost evidence, etc. Trying to discover the truth now is like trying to use a bloodhound to track someone who walked through Grand Central Station in 1963.
Fourth, a series of events took place that made the Kennedy assassination the most tantalizing mystery in US history. It happened in front of millions of people; there were videos and photos of it; the murderer wasn't seen by anyone at the time of the assassination; he got murdered a couple of days later by a guy who later died of cancer. It's a cottage industry that probably brings in more money than Roswell, the Loch Ness monster and Harry Potter combined. There will always be another theory, as long as there's a buck to be made.
And a sucker willing to part with his money.