In your opinion how did the open world format work for pokemon legends of arceus? Is there anything you would have changed about it?
TLDR, i think it worked fantastically. but in order to get into why, i think i need to get into why the open world of SV (and to a lesser extent swsh) did NOT work.
It's practically one of my mantras at this point, but an open world game can have an explorable space as big as the real world itself; it's not going to be fun to play if it's not worth exploring. that means having interesting locales, secrets and new abilities to find, and exciting challenges to seek out.
Scarlet and violet... Don't really have that. the only thing you can really find in the game are, well, pokemon. Yeah yeah I know there's trainers and the treasures of ruin and maybe a raid battle, but overwhelmingly what you're finding in that big open world is pokemon. And the fun of discovering them sort of pales when really all you can do with that discovery is add them to your team or your dex. Plus, unlike classic pokemon games, the removal of random encounters means there's no real reason to even engage with the pokemon you see once you're at a high enough level and have them in the dex. seriously, once you realize how much of SV is just walking around pokemon in the open world, you'll never unsee it
you could argue that having the choice to complete the 3 stories in any order you like is one of the things you can find. But when all of those events are tied to a structured level scale that doesn't change, your "choice" comes down to either running into fights that are way too hard and then abruptly way too easy, or playing in the exact order they want you to. not exactly enticing either way. Scarlet and violet probably would have just been better off as a more linear pokemon with typical hallway routes instead of spending all this time on an open world that rarely enhances any part of the experience (though i will admit running around with a friend in union circle is really fun)
ANYWAY to get back to what you actually asked, Legends arceus sidestepped this issue by making interacting with pokemon the entire gameplay loop. it was a stroke of genius to make completing the pokedex the main goal of the game, because unlike in the regular series, catching a pokemon does not tie the bow on it. No, in order to advance in the game and truly fill out the dex, you have to complete research tasks related to that pokemon. Hitting it with certain attacks, using items, number caught, number stunned, using certain moves, and so many more. some of them even have side-quests associated with them!
all of this encourages you to do more with the entirety of the world you're exploring than SV offered. switching up your team and trying new things to fill out dex entries is encouraged and gives so much variety to the actual experience of playing the game like you usually would. While there's actually less pokemon to find than in SV or swsh, improving the way you actually engage with all of them makes legends much more exciting to run around in.
not to mention, the game feel in legends is just better, flat out. walking around feels better, the ride pokemon are more fun, pokemon running from you or attacking you feels more immersive than the way they mostly just exist waddling around in the other switch games. It helps that legends, while having some performance issues, is nowhere near as bad as SV has it.
of course, the truth of the matter is that legends arceus is not truly an open world game. It's a series of large and open but disconnected areas accessible from a main hub, rather than one large contiguous gamespace. remoraid to my head, i think i'd pick the former every time. it gives the game more focused central game design and cuts out a lot of extra transient elements that don't really add that much. Running around a true open world is fun and all, but legends arceus would not have been a better game just because you could walk directly from one area to another, much in the same way that Scarlet and violet really aren't better games for it either
as for what i'd change? honestly? nothing. the gameplay loop of legends was so addicting that i did almost nothing but play it for weeks when it first came out. it was and is the best pokemon game in over a decade. in some ways i can't believe it's actually as good as it is. i remember being so anxious with a friend that it was going to be a disaster when it ended up being a masterpiece.
no, wait, what i'd change is game freak's awful habit of adding cool new features, like this entire game, and then never touching them again. make a sequel. pokemon legends kyurem. call me mr iwao i can make this work