Google got rid of that syntax about a decade ago, when they were trying to make Google Plus a thing. (As I recall, they wanted to reserve it for G+ usernames, like using @ for Twitter or Instagram.) I just checked and it looks like they still haven't brought it back.

They "new" syntax is to surround the desired term with double quotes. But of course quoting was already used for searching phrases, so autosuggestions stopped working for phrase searches. Progress!

It's easy to see why they wouldn't reintroduce power user tools once removed. It's sucky, but all mass-market tech is like this, constantly adapting to fit some lowest common denominator. Power users just aren't that.