It is very hard to maintain the profitability of a podcast. To get around adblockers, many podcasters have taken to editing the ads into the podcast before the podcast is uploaded to any platform. I suspect this may be the case for some of the instances you mention. These ads are not added by Spotify or any third party. The podcaster either does a sponsored ad-read or receives the audio/video for the ad from a sponsor and adds it to the podcast in post. Not much you can do at that point other than watch the cast on YouTube and use SponsorBlock.
It works fine for me fwiw