Low player number is not result of showing amount.
Player number dropped a lot after big changes, like when protection removed at capitals.
Show player number or not will be same problem.
When games change a lot in test is normal to lose many player as change not way they wanted. Can only please some people not all, whatever change some will leave or take break.
Also game is test for very long time, people lose interest and hope. New games always come that fill gap in time that was spent in Naval Action.