I agree with a little of what you say, some of it for slightly different reasons:

Huge Amounts of Pointless Time Sinks - I actually am not too bothered by the things you've brought up but I do have my own gripes about travel and also split zones. I don't like the thing of having to do 6 FATEs to upgrade chocobo speed. Namely, because the chocobo speed is so slow that getting to those FATEs before they're finished, with enough time to get gold on them, is a pain. IMO it would be better to have the faster speed from the off and maybe gate an Aether Current behind the first tier of Shared FATEs instead. This was compounded by split zones, where I would start heading to a FATE to find it was locked behind an invisible wall. One split zone per expansion at most in future is something I would like to see, if they must do them at all.

Too Much Doom and Gloom - I actually think they did a great job of balancing things here. Yes, there are dark moments, bleak moments but it never descends into misery porn, which some games absolutely would have at that point. Garlemald in particular hits a couple of very dark moments but then we help reunite a family for instance. And isn't that the theme of EW, yes, there are bad times and bad things happen but also good times and good deeds? As to Zenos, I'll grant you that one. The last fight with him upset the pacing for me at that point. I would have also liked the option of simply walking away from him.

Dumb Dialogue - Whilst I felt there were a couple of cringey moments on other parts of the story, I don't think it was all that dumb. Garlemald in particular, it actually made sense. These were a proud people who were sure that a plan was in place that would see the empire rise again. Why would they accept that the "barbarians" who, in their eyes, had victimised them historically to the extent that they set forth and found Garlemald, suddenly want to help them? From their point of view, we were there to take advantage of the disaster that had struck them, trying to subjugate them again before they could regroup, spreading lies to make them think the situation was worse than it was.