Outline planning had been agreed. Liverpool Waters is 8 years into a 20 year plan. While the Everton ground dramatically speeds up the timeline, don't fall into the trap assuming that no visible action means there is nothing going on.
Its fair to assume that we all (at least most) agree the best thing for BMD is for the stadium to be built, for many reasons, selfish ones and for the positive effect it will have on the economy of the immediate area and beyond. However, it is best to understand your opponents. The argument of HE, is not that the dock should remain derelict, but that the dock should be used for the purposes as was signed off in outline planning at the beginning of the decade, a residential use maintaining a water presence and being recognisable as a dock. The time it would take is not the issue for them, clearly.
However, I would say that in the wording they have used, they accept that it is difficult to argue against the stadium when comparing their concerns against economic value.
Best thing we can all do, is to respond to the planning update, and make it clear that more money will likely be spent, and the positives it will give for the city as a whole. Also a good opportunity for people from abroad to talk about how they will visit etc etc.