Plat is literally above average. If you look at the this rank distrubution chart from 2018
A 2500 Player would be around the top 40% of the playerbase (average or slightly above average)
And someone around 2999 would literally be at the top 15% of the playerbase (not an elite player but definitely better than most players)
So how exactly is Plat “below average?” 
And before you comment “This doesn’t count because it’s too outdated!” Do you have a better & current rank distribution list which would prove that Plat is indeed below average? I’ll wait 
(And no, personal opinions towards certain ranks don’t count. Otherwise anyone below 4.4K would be “low ELO” according to certain pro players)