Are saying that things never improve? I really think your saying that they aren't good , means that things can't be better. In the system they were in, standing around, not being aggressive, might have lead them to appear that way.
All the upperclassmen would probably say there is nothing they are doing now, that compares to the way it was before. This team should turn a!ot of heads , anyone who thinks this is not true, is not paying attention.
Defensively, after playing multiple years of college basketball, I think they are what they are. BU's system isn't going to magically make them faster or more athletic. While Groce had a pretty mediocre offensive system, his defensive system was pretty respectable. And if anything, you need more speed and athleticism in BU's system.
So no, I don't expect Finke and Black to suddenly be good defenders, simply because they don't have the physical traits to do it. But that doesn't mean the team can't still be much better than last year.