FWIW, I think there is some confusion on the topic, both on this thread and in general. Media is also partly to blame for this.
Scheme
What is a defense scheme? Scheme is basically our defense strategy, or what type of defensive formations we use (3-4, 4-3 etc) against different offensive formations and teams. Basically our base defensive formation against any given offensive formation and team.
Formation
Or defensive line up, 3-4, 4-3 etc
Play call
The play call is the formation and positioning (inside/ outside), cover (man, zone) special responsibility (blitz etc) etc within the called formation like the 4-3.
Reads
Reads are the individual player responsibly for the players within the called play, like who got the QB, RB etc on option plays, who got the WR's in trips etc. Reads can be very complex and it takes years of practice and playing for the players to not think about reads, but to react automatically.
So, have we simplified our scheme?
My answer to that is no, but we have changed our use of formations somewhat. We are playing less 3-4 and more 4-3 or variations of the 3-4. The reason is IMO that we still don't have the DL or OLB to play a true 3-4. Have we called fewer different plays? From what I have seen, the answer is no. What we seemed to have done is to tweaked our use of formations within our scheme and simplified the reads, playing more 4-3 base defense with added blitzes.
Why have we made this change?
Lack of depth and experience. A senior or rs senior would have no problem playing within the full range of our scheme, but when you have as many young players as we do, it only takes one of them to miss an assignment/ read and the whole defense looks bad. Lack of depth is off course also a reason.
Why haven't coaches done this change during camp?
It's always easy to have 20-20 hindsight. What I believe to be the reason is our lack of depth and inexperience. It's easy to look good going against your own scout team, but it's a different ballgame going against teams with experienced players and play callers. A read made in practice is missed in the game, because what our players sees isn't exactly what he saw in practice and the reason is inexperience IMO.
So, we have simplified the defense with more use of base defense which reduces the number of reads our players have to make, but our scheme or defensive strategy haven't changed. You can say our defense now is more vanilla.
FWIW.