Fair enough. I'm not saying that the ST coach is not part of the problem. I'd have him ranked as the last part of the equation.
The biggest part of the problem is McVay. Looking anywhere else is not going to move the needle in changing anything.
I'm not sure if you saw the NY Times article by Mike Sando regarding ST posted on this board today, but it was damning. It measured five key metrics: core special teamers, depth ST rate, depth ST degree, low-use players, and starters who played on special teams. The Rams ranked 31 out of 32. It also mentioned that McVay doesn't devote much practice time or meeting time to ST.
There is no coach who can make up for these shortcomings. Sure, change the ST coach. It won't make a difference until McVay actually invests real resources, time, and energy into improving that unit.