I think Jones understands the technicalities of the game, I don't believe he is very good at the man management side of things. Ultimately, there is no sport in which going well for the world cup is predicated on being **** beforehand. There is such a thing as peaking but it's not like you have to see a huge drop in form in the interim years. Maybe not maintaining the same high level but to be setting record worst performances? Nah.
I don't doubt Jones has a plan for the world cup, what I doubt is that he is making it work or that the players are fully buying into it. An unworkable plan is as good as no plan at all. As has been said, plans are all well and good until they are put to the real test. At the moment we are failing at the real test. The basics are WAY off and, unless Jones is constantly telling players to frantically throw the ball about when under pressure, give away tons of penalties, drop scrums, knock on, get isolated, not be close enough to clear out, consistently leave gaping holes on the wing, fail to chase back, not play to the ref etc, then something is clearly going wrong. These are basics which should not require any coaching at international level so, in my opinion, point to a mentality problem.
There is no smoke without fire. Jones through his entire coaching career has had accusations levelled against him about being a control freak, a workaholic, being unable to take criticism or challenges and burning people out. This is not just with England. Now ask yourself what would a side suffering from the above look like and just how far off that are England right now?