Dear @rszama, let me add one more voice of concern to the discussion. While many of the points you make are fair and commendable, I believe there is a logical leap in your reasoning when it comes to justifying the existing solution.
Integrations are useful, no arguing that. They can also be an important source of revenue for big projects, in turn ensuring the projects thrive and continue evolving, again a positive. Getting the word out that the integrations exist, to the right ears, is difficult - this is the real problem you are trying to solve. But is the current "ad" solution the right one, is it appropriate for the audience it is being displayed to, or compatible with the ethos of the Drupal project in general? Here is what is wrong:
Targeting (who is seeing the ad vs. who it is really addressed to): Currently the ad is seen by developers working on the platform, and in unfortunate scenarios it could also be seen by the client's administrative staff, potentially leading to all sorts of awkward scenarios. Do any of these people actually have a say on whether the client or agency contract such a service? Not likely. The real decision-makers that need this info (the client's product owner and the contractor's architects) will never visit these pages where the ads are displayed.
Repetition: The ads stay there, outliving their usefulness and becoming a nuisance. The devs will see them the first time, get the info, and if they can relate to it, they will relay the info to the decision makers to communicate it further. If they ever intended to do anything with the info, they'll do it during their first few interactions with the ad. Afterwards, it becomes noise at best, irrelevant information in already busy UI screens, distracting you from doing your daily work.
Drupal spirit: imagine if the top 1% of contrib modules adopted the practice of putting just one discrete ad each in their admin pages. Just picture what the develeloper's experience would be, constantly navigating across all these discrete little ads here and there, trying to get work done. Is there a single person around there that would welcome this future?
I'm also in the off-by-default camp. But if you need to go for a togglable, on-by-default setting, at least add a very clear CTA on the ad itself, in the lines of "Got it. Hide this ad from now on, I can always re-enable it in the XYZ settings." We will still see it when first configuring the module in a new project, but we should be able to very quickly dismiss it thereafter and get on with our work without further disruption.