Individually, you can argue that almost all the players on the roster are good. And very few seem to have 'given up'. However, almost every player has had a 'breakdown' at some point, whether it was a bad penalty, a missed coverage, a blown pass route or blocking assignment, or whatever.
With the defence, the breakdowns mostly cluster into the latter stages of the game, and can be attributed to frustration, despair, exhaustion, or trying too hard. The defence, in my opinion, has the personnel to do the job right now (although maybe not the depth). I'd single out Brooks, Cox, Peterson, Hitch, Goss, Cody, and Young for particular praise, but I'm probably being unfair to some others.
With the offence, I don't know what the problem is. They're simply out of sync, which makes them all look bad, even thought the talent is there. They had it together for one drive last night, and look what happened. But then it all fell apart again as soon as one little thing went wrong. I commented last year that I felt the team was 'brittle', and sagged as soon as a single setback came up. I think that has to do with confidence, and has to be laid at Marshall's door. Lancaster can't change the psychology of the team overnight.
That said, I think that most of the pieces are there to build a good offence, as long as the confidence problem is sorted. Ranek and Radelin have played well, as have most of the receivers (Hill will be an upgrade over Cavil). The line has some good talent, but can't seem to get it together for more than about two series (WInnipeg game excepted). QB is currently a question -- Maas can't seem to hit the long ball, and Eakin looks unconvincing when he's in. However both have had success before. Is it injury? Is it the schemes? Is the playbook simply too complex?