The more time I spend making videos and in particular watching them on YouTube I can clearly see that it doesn't matter how much gear you have be it 1080 or 4K, it's not the quality of the video that makes people watch it, but rather the content.
You only have a minute or less, probably more like 10-15 seconds to grab the viewers attention; coupled to a catchy headline and thumbnail that got the viewers attention in the first place.
I often see some amazing footage on YouTube probably taken from a DJI Phantom 4 in 4K and think WOW! if I had one of those, imagine how many people would watch my videos and how much advertising revenue I would make!
If you're taking 4K documentaries, different story completely. The difference unlike YouTube is that you might get a 30 second timeslot to advertise your movie in the hope that it will grab a potential viewers attention.
Long story short... if you are good looking, funny, famous, have some good content and nice sandy beaches with blue Caribbean waters, you could film it on an iPhone 6 and people would still love it....!