Numbers of pilots online in my primary game time would like to have a conversation with you about this.
Several years back it was not uncommon in my primary game time to see 35,000 to 40,000 pilots online when I logged in, today 18,000 to 20,000 during that same time is normal. No doubt there are a number of reasons for this drop, but players leaving the game is definitely a part of that.
Many alpha players start this game because free to play and then quickly realize that without spending money to sub they have no realistic chance of competing in any of the games activities so they quit. Veteran players are leaving because they grow tired of CCP changing the game simply to cater to new or alpha state players removing the challenge and enjoyment from things they have been doing for years.
Perhaps nul sec is the most visible aspect of these problems. CCP has made wholesale changes to null and the ships used there in a vain and desperate attempt to breathe life back into their signature area of space and yet, it is just as dull, boring and stagnant as it was years ago, back before they started trying to make it better.