That only worked when we we shipping sugar, cotton, etc. in - and local / North of England manufactured goods out.
There IS no North of England manufacturing
WW1 and The first lot of American debt seen us off.
WW2 gave us a short term lifeline - but no real Investment
Changing / Emerging world trade patterns meant the port was a deadman walking.
Lack of investment in the 50s and 60...(for instance, when Dunlops shut in the early 70s they were still using the same machines the arl lady used to make tyres for Halifax bombers in 1944.) The EU and general 'events' plus Thatcher did the rest.
Those 7miles of docks mostly don't even exist now in any usable form - ships are bigger, containers are the way.
Dockers hooks are in museums along with gas mantle trimmers and such.
Any increase in trade from westerly direction will and does go to Southampton, which sadly, is much nearer to the SE where all the people and money are than Liverpool
Any North Docks regeneration will be retail / sevice / Commercial and private accomodation driven.