How relevant is domain authority?
 

Hello.
I am currently trying to pick a keyword for my website and have found something that I think looks good. The page authority of the top sites are around 40ish with the average juice links at about 30.... The moz rankings are also fairly low.

The thing I am worried about is that most of the websites are wikihow and youtube and have a domain authority of 93 and 100. Is this just a really trusted site having 1 article about the niche I want to get into? And if so is it easy to beat them? As they have low links and page authority, surely if I had a whole website dedicated to the niche google would like it more?

p.s: The youtube links have a page authority of 1 with 0 links and a domain authority of 100. What does this mean?

Thanks for your time.