To me, the point of scrimmages is practice. You work on key things, to see what you have, and get all your kids experience and reps. Same thing with benefit games.
Yes, you can see some athletic ability, but I can't say you can really tell anything about the coaching. The only time coaching may come into it is a new coach and seeing what they are running. The point of a scrimmage isn't to win. I'm sure some look at it that way, but those are usually the ones looking at it the wrong way.
I can't remember who the teams were, but recently (last few years) I remember a thread about 2 teams that had scrimmages that year and met in playoffs. The talk was Team A "won" the scrimmage convincingly so they were going to win the real game, it was a big blowout in Team B favor