Iron Maiden are where they've always been and they are still going strong. To be honest, I don't want billions of kids who don't know musicianship and proper music watching their music videos. I'm happy to leave them to their easily digestable formulaic generic pop hits. Let a few of the lucky ones find Iron Maiden when their tastes mature and they go searching for authentic music.
I say this as someone who doesn't care for pretty much anything mainstream: get over yourself. This music is for tweens & young teens, which is why it dominates YouTube. There is plenty of good music today, but it's not what tweens listen to, because tweens have always liked and will always like cheesy, mass-marketed stuff. Every generation detests the culture of the one that follows it. Your parents probably think what you like is stupid, and their parents thought the Beatles were stupid. Katy Perry's music is terrible...but so what? You really resent 13-year-old girls dancing to it in their bedrooms? This is somehow a problem for you? Let them have a little fun. There will always be someone who can look down on what you enjoy. Maybe instead you just let people enjoy themselves.
In your opinion, what you call good music is good for you, whereas other people would find current music good. You only think your music is 'good' because it is the music from your youth, and it may bring back happy memories. I am 16 years old, and the music I like most is chart music from around 2006 to 2014, although I like some current music too, however I do find that some music recently I haven't enjoyed whatsoever. This is because it isn't similar to the music I listened to when I was younger, therefore it sounds strange and new, not familiar to me, thus I "don't like current music". Keep your opinions to yourself, and don't go spreading hate, there is already enough of that in the world to go around.