It was the first defense that was built to counter the spread, and the modern 4-2-5 benefits from a lot of the innovations Gary Patterson made at TCU to simplify on-field adjustments (that way teams are less vulnerable to tempo).
Where 4-2-5 tends to struggle is against RPO schemes because it’s very speed and aggression based. Essentially, because it relies on immediately responding to what the offense shows, it struggles against dynamic schemes.
Therefore, Rossi and crew have countered with “get more nimble everywhere you can”: The most prominent place you see this is using OLB types as rush ends more frequently. This was the role that Oliver played for us last year, and also one of the primary reasons Coughlin moved to EDGE (and Thomas Rush is moving to EDGE). The game slows down for them closer to the line and allows them to use their athleticism to offset the downside of aggression.
I expect see more of our larger SDE recruits (like Deven Eastern) also getting slid to 3-tech DT roles over the next couple of years. Of course, the key is landing a solid 0-tech, because a space eater is critical to an effective 4-2-5. MDT played that role for us last year and will again this year, but beyond Jamaal Teague we dont have great depth there.