American Express does not really communicate about the <Amex lounges>, partly because it was only a few, and so not really a "benefit" ...

I think I was never in an Amex lounge, and if I was, I didn't notice it was one

Amex offers mainly complimentary membership in Priority Pass, at different levels, to Platinum and Centurion card holders. I don't think it was ever offerred to Gold card members.