Someone else might not constantly drop Joseph Ossai into coverage.
Now, that's snarky on my part. I think the essence of your point is true. The players are terrible, and a change at DC would be unlikely to net massive improvement right away. However, I do think some improvement is plausible. Golden's defense has truly achieved the impossible: be worse than 2024. That's just about the one thing he could not let happen, and it has happened.
Regardless, meaningful progress is unlikely if they continue to miss on a staggering proportion of their draft choices every year. It all returns to Tobin for me (and the ownership family by extension for giving him permanent, unquestioning job security). The owners can't be fired, but Tobin can. It would require a huge break from Bengals normalcy, but I think it's plausible for the noise in the fanbase and national media to put pressure on them.