I have only been using Steem for just over a month & have to say from my limited knowledge so far that I agree with what you have said here. Some of the folks who started the same time as me have treated it like an ATM & hey presto those are the ones that are no longer here.
All of my activity so far has been to power up every little cent earned & into growing a reputation to move forward with as I see today's minnows as tomorrows whales.
I read the other day that from all those who started in January 2017, only 7.5 percent have posted in the last 6 weeks. Quite incredible. People may see this as a retention problem of the platform, I see this as more an intention problem of the users.
Yes folks think its Facebook & it isn't, Once they realize that there is real work involved in growing a half decent account they up sticks.
lol, 'up sticks' is a term long unheard.