I generally don't accept the result of studies which claim "If we had replaced W with X, we would save Y amount of Z." IMO, there are too many variables involve

I generally don't accept the result of studies which claim "If we had replaced W with X, we would save Y amount of Z." IMO, there are too many variables involved to make such assertions. The models for coming to such conclusions are way too simplistic. For the same reason, I don't even buy retrospective arguments like "We switched from W to X and ended up with Y fewer/more of Z." It reminds me of TypeScript mania when companies where claiming "We switched from JavaScript to TypeScript and reduced bugs by X%." It's nonsense. They could probably have reduced bugs by X% merely by rewriting the project, even if they stuck with JavaScript. Rewrites are almost always much better than the first iteration, simply because developers learned what the issues and pain points were and were better equipped to avoid them during the rewrite.