Personally I don't think that Dragon's Dogma would have worked as well without the semi free roaming aspect. While it's true that running around the same areas over and over again kinda got tiring after a while (especially during a second playthrough), the game works well because the first time you explore the maps you absolutely have no idea what's gonna happen and the idea of an open world gives with your expectations in a rather nice way.
There aren't many games like Dragon's Dogma but something similar without a party and a "linear" experience are Severance, Dark Messiah and Enclave. In my opinion Dragon's Dogma managed to add exploration done right especially if you happened to start some quests at night. Of course there's room for improvement but ultimately I feel that the open world and the day night cycle were mandatory for a nice experience.
I do not disagree that the open world works well initially, for the reasons you cite, but to me it ended up feeling too constrained too soon.
The main world map in DDDA is neither very large nor very open to begin with, broken up as it is in a handful of expansive areas connected by choke-points and shortcuts, plus several more separate maps hidden behind loading screens. Now, I'll take a small but high-quality and smartly structured map over a massive empty bland expanse any day, but the world in DDDA, while not barren and filled with nice small touches, is also mainly a collection of mission hotspots connected by mostly trash mob fights, and not a lot of life to give it a sense of authenticity (a duchy with one city, one village, and a handful of ruined forts). The basic enemy types feel different and come with their own unique challenges, which keeps battles fresh for a good long while, but are repeated interminably and then replaced by reskinned versions of themselves ad nauseam.
I too have good memories of initially exploring the map, such as wandering along the coast and stumbling into my first golem, which IIRC took me one and a half in-game days to defeat. By 1/3 of the way in, though, I'd explored everything but BBI and the Everfall and was left disappointed by the constrained nature of the map.
I actually liked many things about the world design. It has generally good, consistent art direction. Some places are distinctive and many are atmospheric. There is a good use of height and natural obstacles. I just wish that all that effort had been put into something more focused and varied, such as individual areas connected by an abstract overland map, a "linear open world" experience such as the Souls games, a hub-and-missions structure like that of the DX games, or even a BBI-style dungeon crawl but with more, larger maps and more interconnected hubs. Anything that could put the limited budget to better use than trying to make an open world. Such a game would likely be shorter, but more balanced and more replayable. The combat system is very flexible and adaptable, and would not suffer in the transition.
The day/night cycle is indeed implemented very well (Bethesda and almost everyone else could learn a thing or two) and probably wouldn't work quite as well without the open world. I think that would be acceptable but YMMV.
Sure, it's possible I'm just deluded and to sell this kind of game these days you do need an open world and a minimum of 100 hours of running time, no matter how repetitive, so the only way Capcom could have improved the game would have been to invest more money in a richer gameworld. Or maybe all my not-open-world ideas wouldn't actually save as much of the budget as I think, and the game resulting from my alternatives would turn out very short without being much more varied. I still enjoyed the game for over 100 hours as it is, even with all the repetition and the broken balance. "Great but flawed" is, after all, the best we get in the best of times.