YouTube videos are great -if- the problem you're having is exactly the same as the problem the YouTuber is solving. For example, I was able to replace the HDMI capacitors on my A/V receiver because I lucked upon a YT video where the problem I was having was identical to the problem the YouTuber was solving. So it was basically, buy these capacitors, replace them, and off you go. Repair usually just requires basic soldering skills and the ability to put things back together you took apart.

When the problem is not exactly the same, I'm just lost. There is not a lot of diagnosis videos on YouTube. All the videos are: "1. I observed this problem. 2. [???] 3. I'll walk you through soldering on the new components." skipping the most important step 2.

Same for car repair videos: "I see Problem X happening. Problem X usually means component Y has failed. Here's how to replace component Y. The end." If that doesn't work, you wasted money on the part and your time ripping apart your car and putting it back together.