I get what you mean. I don't think autocomplete has changed radically either, which isn't necessarily a bad thing.
What autocomplete/editor were you using when you felt the productivity gain was mostly a placebo? I've mostly used it in VS Code and a bit in Antigravity.
I predominantly used GitHub's product (it had integrations for VS, VS code, jetbrains), and Supermaven. Later, I tried one of the earlier Cursor versions as well.