The YouTube algorithm panders mostly to the "quantity over quality" mindset, meaning the more low quality videos you put out, the more likely they are to be recommended due to there being more of them. Its a really stupid concept, but that's just how it works, so creators who put massive amounts of time into their content aren't as recognized as people like steveee who mass produce these minute-long clips. Its been like this for years and its probably never going to change.
Regarding the titles/descriptions not claiming he made it - While at first glance it may not seem like anything wrong, as nowhere does he directly claim that he made the content, the style of videos are almost like a showcase; the whole concept around the videos is basing it off of one resource pack, mod, etc. Due to this style of content basically being a showcase, by not crediting the thing you are showcasing, he is basically taking credit for it. He even has a few videos titled "I shouldn't have done this" or something similar, which implies that he๏ปฟ is the one who did the thing, and its pretty evident from the comments that the viewers also think this.
If you look at the comments, you'll see a lot of people who think all of these packs are his due to this. Some even ask him to publish the packs, not knowing that they aren't his and are already out there. If it weren't for the style of video he makes being showcase heavy, it wouldn't be an issue. Lots of other creators simply use packs as they play, but since the content they make doesn't directly revolve around the packs, there isn't completely a need to credit (I've seen a few cases where if someone in the comments asks what the pack is, the creator will respond directly with a link, which is good).
Crediting these packs takes almost no effort, as a link in the description is all that is needed, and would help out the pack creators a ton. An example I used in another comment is that even if 1% of the views on that video clicked the link/downloaded the pack, that would still be hundreds if not thousands of people, which would help the pack creators out tremendously.
TL;DR - The large number of little things combine to form the larger problem that this thread is about. It could be argued that he isn't doing anything wrong, but all of these factors make up the larger picture.
