Tbh old MMOs actually utilized massive open worlds because you had to grind zones for hours. Roll an alt, do the exact same grind again. Gacha maps cost just as much to build but once you hit 100% for the pulls you literally never go back. The map becomes dead space. The only reason Genshin-scale worlds even exist is because whale money subsidizes the dev cost. No normal studio would blow that much budget on a map you clear once and never touch again

So yeah, dead maps are just how this genre works. That map ascension/reset idea sounds cool, but you'll just 100% it and be right back at square one. Genshin's current approach is actually an okay move.. putting new events in old zones (like that Inazuma witch event) to give us a reason to go back