Personally, I thought it was the most enjoyable open world I've explored all generation. The art design is certainly a primary reason why I was so captivated by just picking a direction and seeing where it went. I didn't feel particularly compelled to explore every nook in cranny in Breath of the Wild, for example, because, to be honest, I didn't find the world as visually engaging. I loved BoTW, but perhaps it was the shallow combat that made exploring Hyrule not as exciting as I was expecting. For example, in GoT, I didn't mind when my exploration was interrupted by bandits or mongols, because the combat in that game is so damn fun and satisfying. In BoTW for example, running into an enemy mob was more of a nuisance, because most of the time I was worried about wasting my really cool sword on a trash mob, so I avoided combat outside of main encounters as much as I could (I wanted to save my best weapons for "real challenges").
Tsushima was also so visually distinct in each location that I never felt like I was suffering from asset repetition. Sure, the interiors of homes were pretty much the same in terms of assets, if not layouts, but the locations themselves screamed history and character. During my first playthrough of the game, I literally sunk over 20 hours into the game just exploring, having only completed 3 main story missions (one so I could have access to stealth kills, and the other, so I could have access to the bow, and I think just one extra one after that). I was so captivated by the world, and how alive everything felt, that I just got sidetracked so much by the extras. Not to mention any random sidequests I uncovered that aren't marked on the map (of which there are plenty, as many of them only pop up if you either clear a mongol camp, or talk to an NPC that tells you about a point of interest).
Question marks on a map isn't an "Ubisoft style" map. It's a standard of the open world genre these days. I personally don't have a problem with them, it's only when there is such an overwhelming amount of them on the screen, like in The Witcher 3, or Assassin's Creed games, that it can sometimes feel too much, but even then, none of us are actually forced to engage with them.
I'm currently playing through GoT on Lethal difficulty, and in this playthrough, I've completely disregarded using the map at all. I've just been hopping on my horse and riding in a direction, with the sole exception of specifically getting the more resource charm as soon as I was able to free roam, as I knew that I'd want to upgrade my gear as quickly as I could because of the higher difficulty level. Outside of that one shrine, I've just been roaming the land like a wandering samurai, and since I don't have the pressure of wanting to play through the story to avoid spoilers, I'm able to just soak in the world at a more leisurely pace. It's made this second playthrough just as enjoyable as the first, if not moreso. I've already platinumed the game, and collected 100% of everything you can collect during that first playthrough, so now I'm just allowing myself to soak in all of the beautiful scenery and visual storytelling the game has packed into it.
For me, not every square inch of a game needs to have some kind of content or deeper purpose to it. The biggest example I can give from my gaming experiences is Shadow of the Colossus. That game is nothing but 16 boss battles, and a large expanse of land between each encounter, yet I spent countless hours just roaming around on Agro, scouring every nook and cranny, not because I expected to find anything like side quests and missions, but because the world itself was so beautiful and haunting and mysterious, and I just wanted to see it all.
I don't particularly suffer from OCD, so unfulfilled "?" on the map don't bother me, and I never feel like I'm forced to pursue them and check them off of a list. I enjoy the AC games. I enjoyed Day's Gone, Horizon, Ghost of Tsushima, The Witcher 3, etc, and it's because I just played the games until I was full, and didn't get obsessed with having to "clear" everything on the map. I find that, for me, at least, it makes my experiences with those style of games much more enjoyable. If I ever find myself getting tired of mindless exploration, I'll tackle a side quest, or a main mission, or maybe I will investigate a nearby question mark to break things up. The beauty of the open world genre is its freedom, and not letting the "gamey" aspects of the experience like map markers and waypoints and question marks make you feel like you just have to follow them. I'm not a fan of checklist gameplay myself depending on the game loop, and the enjoyability of said game loop, but like I said before, I don't think open world games are necessarily forcing you to do that (although AC does have the issue of Level requirements for some missions, when can make you feel the need to grind levels, but even then, I've cleared missions that I was "underleveled" for in those games, so I think their level requirements are more "suggestions" than actual "you need to be this level to attempt this mission.")
