Actually, the AD links are useful, if you know how to make full use of these links. If you have not exploited these type of links to the max, then yes, they are useless for you - but if you have, then you'll know that the AD links can be used for many specific purposes.
Considering that AD links are on a decline, due to various factors, such as AD owners are now privatising their ADs, and not many would allow it to be used publicly, and furthermore some have employed advanced captcha solving on it, but when AD links are available in a bulk, they are indeed useful.
Primarily, when AD are blasted in gigantic bulk, they can in fact influence a site's SERP, but you'll need to know how to lace that with 301s, redirects, shortened urls, etc, and a lot of other things.
Secondly, a gigantic blast of AD links can also help get your T1 links indexed within 8-24 hours time, and second+third gigantic blasts will make those links stick in indexed status for very long period of time.
Not many tools now support gigantic blasts, but there are a few that are still being sold, but the owner has now stopped updating it for many years now, thus this is yet another factor that is making links from AD on a decline.