9/10 demos are/were not used for blob denial but to casualy wipe a squad here and there, which is cheesy af and way too cost effective. While there's no denying that there need to be effective blob denial tools, demos are not suited for it.
You say that but youtube is full of videos of blobs being utterly annihilated by a demo (there are some great videos). At one point it was pretty much a COH2 meme. That said they were almost always from 4vs4 games, which are always just blob orgies, so that doesn't really count for anything.
I agree that they were OP when you could easily wipe a full vet squad for just 90, that did need to be fixed, but they went too far the other way and now demos are pretty much useless. They need to be given a useful role again, and I think at the very least denying support weapons is a good start.