I used to live in Edinburgh and work just up the road from leith. I vividly remember leith central station was still there. The platforms etc were all in tact and there were still luggage trollies on the platforms
The docks were still heavily used and the millerhill loop was still frequently used. I really enjoyed the run around the line when we got diverted.
In all my years around the area I never remember seeing a train down at the docks. Given that the docks will never again see any meaningful traffic then If line isn't used at all then may as well get lifted.
Also given the antipathy towards local rail services from the regional council it's obvious that the line won't ever see any increase in traffic. Let's face it if they aren't interested in opening the loop what chance have any other lines got. The loop should have reopened,years ago instead of the useless tram service.
Leith has seen its time when it comes to trains. Politics and indifference have seen to that Sadly