So having finally caught up with the MSQ:
I can see why a lot of people are frustrated and it might be that I binged a lot of the MSQ recently but I see a hell of a lot of moving pieces being set up here and some peoples concerns miss some huge things that have been implicated.

First and for most is the issue with the balance between the Light and Dark. We know we cant deal with the Ascians yet because if we do we trigger a flood of light and lose. My suspicion is the thinning of aether is the first sign of a flood of Light approaching. That means even just beating the Garleans might start it. We need to learn how to solve that before we finally come to a climax against Acians and by proxy, Garlemald.

This last bit, as small as it is, set up a lot of explanation on why we have the time to deal with that. We see that Thancred's idea has paid off and it has forced the Garleans to divert their attention to stabilising their control before pressing against Eorzea again. That gives time for things to brew, including the Black Rose.

We get our in game indication that the Crystal Tower is a way to travel to other shards. As for why, apart from getting our allies back, we are told outright that either outcome of our current war ends in us losing, something which has been very strongly hinted at already and told that the solution lies on the First. That, more than anything else, would be an extremely compelling reason to go there. It is an answer we have needed rather desperately since we found out about the First from Albert.

Finally we see a lot of set up of things happening at home which almost certainly will brew to pay off later. We see Solas, probably possessing his grandson now, seems to have a plan involving the Black Rose and the rising light. My guess is he has seen a potential way of using how the Black Rose is effected by the Light to trigger a Calamity event which would probably cause a lot of rebalancing. I suspect he is hiding this from Elidibus because "he was ever the worrier" and there is a risk in allowing the Light to continue to rise. Ironically, I suspect becoming the WoD will lead to us effectively stopping the next calamity.

Finally we see our old friend, Zenos, still in some poor Elezen's body, and seemingly making the decision to 'reclaim what is his'. I think this will be important in two ways. Firstly he is a massive wildcard and I think he will end up throwing a major wrench in the Ascian's plans, maybe even managing to kill off Elidibus to reclaim his body. Secondly, I could see our final confrontation with Zenos being with him leading Garlemald in 6.X, particularly if Solas is riding in Varis's body and we end up killing Solas next expansion.

One other aspect of this I have been wondering about is if our assumption that it is just the Silvertear lake which is the 'Source' of Aether on Hydaelyn. This makes me a lot more interested in the Crystal Tower as it strike me as something that could very much be a relic of the pre split world or something created on each world when the split happened, sort of like the Aetheric epicentre. It would explain why the tower could be used to travel between the shards.