Ramnut - welcome aboard
It's cool either spelling , this is a UK based site so the defence is applicable even if we are talking about a sport where the offensive spelling is used
I think that a simple defense is easier to install than a basic offense, as the early weeks in NFLE tend to show. However the problem with a new NFL defense is the potential complexity of it. To deal with the complex offenses they face there are probably many more calls and reads to make, that was one of the problems with last years scheme that seemed to be too many reads to make and not enough just reacting to the ball. hopefully Lovie's scheme will let the defensive players rely more on speed and instinct than making a series of reads. However even simple NFL defenses are probably quite complicated and need a lot of learning , even if it's just in the new terminology.
I also think we have a lot of new players as well as a new scheme and getting the chemistry of a team to work is a funny thing. We don't know how all the new faces will work together , which players will emerge as the team leaders and set the tone for the whole defense, we'll need to wait & see