Your point gets into why I think Golding is such an issue. Saban needs someone that can utilize his defense properly and obviously that includes making necessary adjustments. Kirby did that at Alabama, Pruitt did that at Alabama, Golding can't do that at Alabama. It isn't necessarily whether or not Golding can run a good defense, ironically the highest ranked defense he's ever had was at another school.I've not watched UGA enough to know but is Kirby still running Saban's D or has he modified it over the years? I suspect it's the latter, meaning the basic D might be similar, but the tweaks have made it more effective.
BowlCut is obviously a great defensive mind, so there's little chance (in my mind) that Kirby hasn't modified the D considerably. The Venn diagram of the two defenses would certainly have a ton of overlap but the parts that differ may be considerable.
Not suggesting this isn't a Gol*ing issue, in fact, I think the progression Bama lacks wrt stopping modern defenses is due to Gol*ing. Offenses have changed a lot since BowlCut left for UGA.
He needs to be able to manage this scheme though, and it is the most successful defensive scheme in college football for the past 20 years by a long margin.
To elaborate a bit more on Kirby, I looked at the people he's had running his defense at Georgia (four in total). Not only have all out performed Golding, but every single one worked under Saban! Every single one! In one case I believe just as a student assistant and graduate assistant, but Kirby clearly is choosing based on this criteria. This is not just about people who worked with Kirby either, as those stepped into the role in total actually spent more time with Saban.
In terms of Golding, I would refer back to a concern I had when he first got the job. He had 0 Power 5 experience. None. Didn't go to college at a Power 5 school, didn't work for one in any capacity, so this was a huge leap up. By contrast everyone Kirby has hired not only had Power 5 experience but he specifically had experience with Saban's scheme. So if you want to consider where it went wrong, the idea that Golding is just out of his depth doesn't seem far fetched.
If Golding had spent 2 or 3 years under Saban, and had another person like Pruitt or Smart (he instead got Tosh) to steer him in the right direction it is plausible that he realize the potential he has. But it seems Saban has enough other problems that he can't fix what's wrong with Golding. Unfortunately I don't see Golding giving up play calling, or essentially being demoted to co-DC but that's the only way I see this being resolved with Golding still around.
In a way it's like the Jalen Hurts situation, where Hurts was thrust into a situation he hadn't been properly prepared to handle. I don't think what is wrong with Golding can be fixed with him continuing his role. He'd have to take a step back before he can move forward.