It's the internet, everyone is an expert in everything! Seriously, YouTube has democratized so many repairs and made so many people "knowledgeable" in areas they don't understand.
There are some super-sharp guys on BITOG. There are many more people who just regurgitate what they've read elsewhere. If a post talks about information gleaned from some other forum or a YouTube video, the poster probably doesn't have a really good grasp.
On one hand, a car is nuts and bolts. Nuts and bolts are easy. Someone assembled the vehicle, someone else can disassemble and reassemble it. It's not much more difficult than that.
Funnily enough, the great equalizer seems to be drum brakes. Ask someone to explain operation, then disassemble and reassemble drum brakes without a YouTube video. It'll tell you a lot about their understanding and ability.
Another one is voltage drop. Ask someone to explain what measuring voltage drop is and then actually measure it. Oh yeah, look at their multimeter too. If it's from Harbor Freight, be very suspicious.
Personally, I went to trade school/OEM training program at a local community college (AAS in automotive technology), spent the better part of a decade at a dealership while taking university classes (BA in management), then moved on to working for automakers. I've worked for two different automakers, both heavily involved in the service sector. That's how I collected all my tools and knowledge.