It's in the "Google Express" app now (both a web app, as well as a "native" app).

I didn't like that change, but it does work just as well now, and keeps all the same features (checking it off, manually adding stuff, sharing with friends/family members, etc...).

I do wish they kept it in keep, and even allowed more "lists". Being able to tell it to add a book to my "reading list" would have been fantastic...