No, I'm an oldie (old enough to have loved The Fly when it came out) and I was amazed by how disappointing the substance was. I love a bit of body horror but this just didn't seem to work, in loads of ways.
Just to pick one thing that annoyed me, what was the point of the Substance if, instead of making her look younger, it just caused her to have to give away half her life to a different, younger person? I thought at first they would be one consciousness in two bodies, but they were just two different people.
It would have been better for her if some random girl scouted by Dennis Quaid had got her job. Then at least she wouldn't have had to gestate her rival.
It turned much of the film into the old sexist cliche that a desire to be beautiful makes women hate one another and incapable of solidarity. Took the pressure off the menz.
But more annoyingly it was just illogical.
But even more annoyingly, the horror was just lame, as if going over the top with blood and battery etc was all it took to create an interesting shock.
And the scene where there were lots of messy dishes and food remains in the flat? It seemed so much of a non sequitur. It wasn't till after I left the cinema that it struck me the only reason for that scene was that it pointlessly echoes the food-messy state of Jess Goldblum's flat in the Fly. That had some sort of rationale, though, because flies love sugar and all that.
And the monster at the end just looked like it was echoing the Elephant Man. All so disappointing.