To be fair, two points. One, DDG isn't perfect in all areas, and has lots of work to do. Their budget is a tiny sliver of what the google search teams is/was, and they are much newer. Some topics get better results than others, and that is to be expected.
Two, the others are referencing controversial opinion content in particular. They are saying that if the search is about something controversial or politically charged, the google result is noticeably lacking. This seems more concerning to many of us because this isn't just a newer search engine not quite up to par, this is the search engine purposefully pushing users into filter bubbles of Googles choosing!
I hope I cleared up the difference between what you are referring to and what the others are talking about. Anecdotally, I can confirm as a heavy youtube user (both web and youtube-dl/mps) that youtube search is also affected. Many searches for things that aren't even that "out there" return no results, even with the exact name of the video. If you don't have the actual link from somewhere else, you can't find it. I think what google is doing is dangerous and a very slippery slope. Many of my datahording friends have been on youtube downloading sprees because they are afraid google is about to memory hole important videos that don't exist anywhere else that is easily accessible.
ps. This is also the nice part of the bangs of ddg. Don't like the ddg results, just do it again with !gyear etc. (vs the google gui way, and I don't even know if googles daterange: operator even works anymore)