What that tells me is that many of the accounts who where in the middle brackets have moved into the oldest bracket. New accounts that have remained active have been created at a lower rate in the last quarter of 2018 and this year than during the bull run. Not very surprising. Activity on Steem has been tied to the price pretty clearly. What that tells me is that a lot of the users who came on board during the bull run were after the money and only it and only as long as it was good in the short term.
What we need is improved user experience and users who come for the great apps that make use of the blockchain's qualities (censorship resistance, possibility of ownership of assets etc.) rather than earning a lot of STEEM from the pool.