There is the problem. You have to choose between growing the platform (voting for new participants) and rewarding old participants for long term engagement. If you only vote new participants then the old leave and the new replace the old and you don't really grow very much in terms of long term engagement.
People post on Steem and then leave after getting their $2 because why post for years on Steem if it's not a meritocracy? Your long term posting isn't valued. A post which is years old doesn't get you anything.
What you said is very true. That's why Steemit Inc. needs to find other reasons for people to want to own Steem. Using Steem tokens as currency is a good reason.