I give Grinch a bit of a pass for last season. You can only really rebuild 1 side of the ball in 1 off-season and Riley correctly chose offense. It's where most of USC's talent was already, he's an offensive coach and most of the portal kids that wanted to come to USC were offensive players.
This year, they concentrated more on defense. Bear Alexander (transfer from Georgia) has been a beast so far. That alone is making the defense better. I don't think USC has had a guy like him since the Pete Carroll days.
From what I've seen so far, his schemes have been pretty good. That's a big part of why they forced so many turnovers last year. He seems like he gets too cute with the defenses he calls though. In the SJSU game, the defense gave up a cheap touchdown before halftime because of it. Tried to call a complex defense with kids, most of whom were playing their first game together.
As I said though, I like what I've seen so far...but we'll see what I think after they've played a good team.