I think Bioware did a much better job with the romances in Inquisition than in previous games. To me the romances don't hinder the plot per se, more so if anything is being hindered its the characters themselves because it really seems that we prefer quantity over quality with everyone wanting a romance catered towards them personally or just having so many romances in general. But as I said before I think Bioware did a much better job with all that in Inquisition than in previous titles.
Also, as a random nitpick. What's with the lack of capes in DA. Capes make everyone look at least 10x more badass. I would totally buy cape DLC. I want my Warrior to look like Guts.
https://www.youtube....h?v=KNUbPRj9TGM
It applies to Thedas too! 
I'd say if anything the more open world style has put all the story elements (both main, side and companion/advisor) on the back seat.
This is also a good point.
I know with the Elder Scroll games, at least from Daggerfall and forward, the main questline is important plotwise, but only a small piece gameplaywise.
With a sandbox world, or even just one with fairly large areas that invite exploration, the main plot automatically becomes a smaller part of the content, percentage-wise if not impact-wise.
Well, I suppose you could just make some large area to explore and just not put anything much there beyond randomly spawned mobs, but how much fun would that be?
However, as soon as you start to add in little special treasures, side quests, rare materials/mobs or profession/character/item-related questlines to fill up the larger world you also make the main quest a smaller part of the overall experience.
Bethesda has chosen to deal with this in the way of having numerous large questlines (mages/fighters/thieves guild questlines, dark brotherhood questline, daedric princes questlines), the main plot being one among the big ones. To the point that the main questline oftenisn't the best story the game provides. They are ok with that though, and doesn't pretend that the main plot is the best part of the game, or its main selling point.
With Inquisition Bioware did take a step in the Elder Scrolls direction, with varying degrees of success.
On the one hand the larger world is welcome (so is jumping btw), at least to me since I like exploring, and they did a fairly good job in making it interesting.
However, with a game that is so heavily character-driven, and where the interactions between the characters is both a focus and one of the main selling points I think making the main plot a smaller part of the game content, in terms of percentage, hurts it more than it would an Elder Scrolls game. Making it feel less significant in a way.
You could perhaps tie more of the exploration and remote areas to the main plot, but that risks going into extending and/or making the main plot convoluted just for sake of length/complexity, not to make a good story.
Where to draw the line in terms of size of the world, content, questlines and impact/significance/length of the main story and how important the characters and their interactions is something Bioware still seems to iterate on and, people being people, we will all have different opinions on when they hit the "right" balance.
In terms of romances overshadowing the main plot I can't see it gameplay/storywise.
I can see how you'd get that impression from the forums though. 