In theory this Houston defense (as well as SF's defense) is what the Eberflus defense is supposed to look like.
Mostly simple 4-man rushes with 7 in zone behind it, with some man variation here and there, but as Aikman put it they basically just line up without much disguise and play their stuff. More than anything the scheme relies on all 11 playing with maximum intensity, rallying to the ball constantly, and playing with full effort all the time.
Houston has elite talent and are obviously very good, but SF has bullshit talent due to injuries and still has a passable, and sometimes even good defense with more or less the same scheme.
The issue with Eberflus in my opinion is that he's very rigid, showing little to no ability to adapt at all, and I think there's a very good chance that most of the players just disliked him based on how he conducted himself and that they didn't really believe in him. Of course if that's the case it completely negates the foundational principle of the scheme, which is to play with 110% effort and intensity at all times.
Instead you're just left with a simplistic scheme with guys who may be giving effort one play and not the next.
So that's why I'm not against a guy like Gannon who has a similar philosophy, although not exactly the same given that he runs something closer to a 3-4 base.