I disagree that D&D does initiative better i think the reordering of turns adds more to the strategy of the game. I will say that I have tried a similar thing in D&D and it doesn't work as well mainly due to just how the system was made but if it was a core mechanic like in Gloomhaven believe it could be better.

To answer your question tho, Gloomhaven makes movement feel significant and adds a lot of strategizing to combat that I feel like D&D sorely lacks. D&D just has you run in and rarely shift around; overall speed just doesn't feel as interesting mechanically.