The only way to disable them is to disable the inbox sorting setting (where it sorts primary, promotional, and social). As it is, it only puts adds in the promotional inbox. The worst thing is, i swear it knows where your mouse is and re sorts your emails so an ad lands right below your mouse, increasing the number of ad clicks and the ad revenue. I've had this happen to be multiple times.
Yep, first thing I do whenever I add an account to Gmail is disable inbox sorting — presto, zero ads. This has been going on for years, but if OP just made a new Gmail account for the first time since 2013ish, it could be the first time they've seen the ads. Feels bad.
If you have a Gmail account with promotional emails, go into your promotional inbox and just mouse around a little bit near the top 10 emails. You'll most likely see it move the ads around