Rushing 3 is the same as rushing none - and static 4 man rushes, i.e. 2 DL, and 2 OLB's, without prensap movement or stunts are easy enough to block, as the OL knows exactly what is coming, and who is coming. At that point, it is all about physical ability - absent any presnap deception, or attempts to manuever the OL out of position, by missing an adjustment.
You can't blitz every snap, and you can't stunt, zone blitz, etc, on every snap - but what we've been witness to with Capers is hell bent for leather blitzes on 2nd down, backed up by 3 man rushes on 3rd down - combined with heavy doses of static rushes most of the time. It's easy to block, the QB has forever, and the secondary gets picked apart.
It is true that at some point our guy has to defeat their guy - but there are a lot of things the DC can do to assist in that.
Capers is capable of dialing up some beautiful blitzes - but his nature is to is to take his foot off the pedal, and sit back in hopes of a pick or incompletion.
As for the "front seven"... we don't have a front seven, we have a front six... and therein lies a lot of the problem with being able to generate consistent pressure when the opposition is passing on run downs - the "jumbo nickel" was a complete disaster in terms of generating any pressure at all, b/c the 2 fat guys in the middle were there to stop the run - the opposing OC, QB, and OL all knew it would essentially be a 2 man rush, i.e. the 2 OLB's flying upfield while the fat guys in the middle just played the dancing bear game.
What you end up with is the worst of all worlds - an insufficient number of players in the box to deal with the run; fat guys that can't rush the passer on run/pass downs, and predictable rushes out of static fronts.