These days there is a so much information online that it seems like there’s nothing you can’t learn on your own. I think this is true to some degree, but there are some caveats.
One is that the medium can constrain the way that information can be communicated. In general people don’t write in the same way that they speak. Things that are written come under greater scrutiny so they are less likely to have technical inaccuracies. This sounds like a good thing but sometimes technical inaccuracies make things easier to understand. This is why I almost never go to wikipedia to understand a technical concept. It’s entirely possible that the same person explaining a concept to me verbally can make me understand something I couldn’t if they were writing the explanation. And the same might be true in the other direction.
Of course the big difference between a video and a conversation is that you can’t ask questions. You can’t direct the course of the discussion. But another difference is the kinds of topics that would be brought up. If someone is uploading a video it’s less likely to be about a speculative idea they are unsure about. Not all conversations are the same either. There’s a kind of information that you really need someone to bring it to you spontaneously, information that you don’t know you don’t know. This doesn’t necessarily happen in all conversations.
Another problem is that sometimes the information hasn’t developed mainstream interest, or there is some incentive to hide that information. The first I’ve encountered with technical problems for technologies that aren’t that popular. The second tends to happen in zero-sum games like day trading, affiliate marketing, poker.
There’s a certain kind of knowledge that you can really only efficiently get through finding the right people and sometimes even building the right relationship with them. And just like finding and consuming published information is a skill on its own, finding and consuming this kind of information is also a skill, and they don’t necessarily overlap that much.
One solution is to involve yourself in communities about the thing you want to know about. But more than just participating, trying to build personal relationships. Another approach that has worked for me is to pay for a tutor. A study group is another idea I think could work but online study groups tend to be hard to sustain.