It seems to me there are really three scenarios:
1. Absolutely Lone Assassin - Oswald.
2. Conspiracy involving others in Dealey Plaza.
a. Oswald as innocent patsy.
b. Oswald as participant.
3. Lone Assassin - Oswald - but conspiracy involving others not in Dealey Plaza.
The CT community seems obsessed with #2, especially 2.a.
I think lots of people, including LBJ, Hoover, RFK, the CIA and Yours Truly, had and would always have at least some level of concern and doubt about #3. The sane conspiracy theories are pretty much all at #3.