none of the other mainline marios have anything like sunshine having a bunch of characters in each level that reappear in different situations every mission, and you can tell they have different personalities, looks, and they may even develop over time like with the lil pianta in ricco harbor that, over time, tosses mario higher and higher. its so wonderful
odyssey comes the closest in terms of worldbuilding as a whole, but it doesnt have anything remotely like this for the people thesmelves. theres a few recurring characters like the desert wanderer, but those reocurring characters hardly have distinct appearances from any other npc of their species. you can only tell this fool is desert wanderer because hes found next to a taxi and a new donker
and thats a problem with how the npcs are designed. teal tostarenans will always be short and will waer the same clothing (with the exceptions of a different hat sometimes), green tostarenans will always be tall and wear the same clothing, and you will not get any other type of tostarenan ever. if you had the desert wanderer in a random group of tostarenans you wouldnt be able to find him because he just looks like every other tostarenan out there...
meanwhile sunshine npcs get a lot of variety even when its so simple. piantas jsut have different genders, skin colors, and then hats, shirts/dresses, and other accessories. that feels so simple but is enough for you to be able to distinguish them!
some odyssey npcs
do have distinct appearnces but it seems to be pretty rare? the style sisters look like every other lochlady, the bonneter biologist(s?) look like every other bonneter. the voleyball coach might even be the
only such unique looking npc but i cant check bc mario wiki isnt cooperative today and i cant open the smo navigation template at all for some reason
and actually.. i just remembered a certain npc in luncheon kingdom. theres a short purple volbonan thats just chilling on a roof who keeps saying theyre not procrastinating (huge mood though) before mysteriously vanishing in the postgame state of the kingdom...
so this one is a reoccuring character that isnt tied to any of the moons and just exists for a funny and adds something to the world. so odyssey CAN do that. it may prove that you dont even necessarily require sunshines structure of having tons of mission per level to have reoccuring minor npcs (though it definitely helps). so why doesnt odyssey have more of that?? why doesnt odyssey give them more distinct appearances??? why cant we have anything like the angry pianta wife in bianco hills that consistently launches mario into the sky for the heck of it
tldr; sunshine has tons of distinct characters in its locations and odyssey, otherwise coming the closest in terms of wordlbuilding, mostly just has npcs. thats all they are
edit: you can also point at just about any sunshine npc and say this is a character with a distinct personality and youd be right! not in odyssey. not in odyssey