It's hard to find content if it's not linked from elsewhere. I understand that building algorithms is hard, and each instance being independent adds challenges. Search will hopefully improve with time.
The best suggestion I could get would be to have manual curation in the app. Have volunteers manually select content for a series of channels that makes high-quality content instantly visible, whether it's vlogs about Linux, discussions of photography, or public domain movies.
Algorithms will probably work well one day, but until then there's nothing wrong with human curation.