I mean I like him, but we don't know what kind of defense he's trying to build really.
It is easy to say the right things. Doesn't matter if your vision doesn't work.
I don't think many fans are blindly thinking he's a great DC without any history or proof of it.
I think why fans are excited or at least optimistic is not because of what he will do, but what he is a part of doing and what we hope he can do.
This team has been following the same gameplan on defense for years. They would bring in experienced (old) coaches who at times had solid to better than average defenses, but none of them were known as great defensive coaches. "Solid" is probably the best compliment you would find to describe them before they were hired.
The end result is this team's defense has been bad for years. Even the Quinn years were heavily compensated by Parsons and the gambling-for-pressure scheme that Quinn ran. It's great when it works, but the moment the Cowboys ran into teams that could block or that eliminated Parsons pressure by double/chip blocking him or running straight at him, the Cowboys defense dropped to below average and absolutely horrible against the run.
The front office has focused on splash pass rushers over the years through the draft and free agency. It's no wonder the team suffered against the run because those guys were brought in for one reason .. sack or pressure the quarterback into making mistakes.
Many fans are excited because they are at least attempting to try something new by overhauling everything.
Sure, it may not work or it may work 2-3 years from now, but even if they have the worst defense in the league, at least it will be for different reasons.
Nolan, Quinn, Zimmer, Eberflus .. those were all the same types of coaches, though I would argue Nolan was the worst and Eberflus was too stuck in his ways. At least Quinn and Zimmer adapted to the players they had some.
What I like about Parker is 1) the defense systems/schemes he's been in, 2) the coaches he has learned under, 3) him stating he has a defensive system but he adapts to what players do best, and 4) details to him matter.
I don't know if he will be a great DC, but the hiring of Parker and the replacements of so many defensive player at least gives fans hope that this defense will be better than last year.
If it doesn't work out that way, then they will be no worse off than we were last year with it because that defense was horrible.