I think when discussing the D being better or worse it's difficult for me to generalize it by saying we lose Tillery so the interior DL will be worse. Or we lose Love so CB will be worse. Or we lose Tranquill and Coney so LB will be worse.
For example, Hinish was playing equal snaps to Bonner last year for a reason. He should only improve this season. Is it fair to think that NT could be better while 3T is worse? If our DE's are better both against the run and pass, how much are we really losing?
Similarly, I realize ILB won't be as good but having a true playmaker at Rover, with Wu, is a significant upgrade. So I don't think it's fair to automatically say "LB won't be as good" when you are dramatically improving one of 3 positions. (Not sure we realize how impactful the Rover position is supposed to be because we haven't had much continuity at the position).
Also, what about the Nickel/Dime packages with Hamilton playing S, Alohi taking the spot of a LB, Wu staying on the field, and Crawford being an X-Factor. Why can't those packages be even better? In fact, in the Nickel/Dime package we are essentially replacing Tranquill, Coney, Love, Tillery and Griffith/Coleman for Hamilton, Wu, Crawford, Hayes, Ade/Ademilola/?. For what that package is used for, I think that can be just as effective (at creating havoc plays) if not better when you figure the pass rush should also be better.
Ultimately, I think the D will look different but that doesn't necessarily mean worse. I bet there will be some statistics that aren't as good. Scoring could be up a bit. Rushing statistics, sure. But havoc rate, sacks, TFL's, INT's, etc. I don't think it's far fetched to think some of those could be better.