In substance, BTC has been a pyramid scheme for a while, but it took some time for them all to adopt the mannerism and language as well. Almost indistinguishable from bitconnect now.
It was taken over by TPTB. Only speculators remained, and only misguided speculators hop on the BTC trainwreck due to the USDT manipulation, BTC is useless for anything else.
It's not true at all, and it's also arguable that nobody ever went broke due to diversification. They're advocating for the quick buck strategy, which is only common in scams/ponzis
I'm actually living proof that it isn't true, as I diversified into BTC during late 2016 and became wealthy quickly because of it. Their faulty logic shows pretty easily