you’re smart and right

That's such a weird critique. It's the same game they played so the experience will be watered down the more they replay it. What were they expecting???

this drives me batshit and i'm glad someone finally said it

I've never even been the type to replay games. I think the only games I can regularly replay are Shadow of the Colossus and Kingdom Hearts 😅

It's funny, because it's like... I personally poured over 600 hours into 100%ing BotW and loved almost all of it (there were moments that pissed me off a bit, like some parts of the Trials of the Sword (the dark room with a meteos wizzrobe can eat my ass) for example, but overall I look back on it fondly). That's more time, I think, than some people who have replayed shorter games like Super Metroid several times over have spent with those games (figuring that the in-game timer for my first SM playthrough where I 100%ed the game was ~14 hours, my 617 hours in BotW are like at least 44 SM replays, which is nearly 2 playthroughs per year, and that's assuming that each playthrough is as long as that one when my non-100% playthrough a few years later was ~6:15 on the in-game timer). And while I know that playtime doesn't correlate to the quality of a game, I think the fact that I enjoyed so much of my time with BotW "makes up" for its lack of replayability (not that it should have to because that's not the point of the genre).

Also there's the fact that games like BotW and ER haven't even been out that long! Open world games, I think, are replayable, but not in the same way as shorter games that expect you to get better and better at the game every time you replay them back to back to back (like Metroid or Bayonetta or Mega Man Zero or whatever), but rather in the "it's been years since I played this so I forget most of the puzzles and secrets" kind of way. And like you say, the same goes for the mystery genre. For example, I recently replayed Ace Attorney 1 for the first time in years, and I'd forgotten enough to still have to think about how to solve some of the cases (or at least remember how to get from point A to point C because I forgot about point B), but I still remembered enough that it wasn't like my first time.

tl;dr: One thorough open world game playthrough is often as long as many replays of a shorter game in a genre known for replayability would be, so the idea that open world games "should" be as replayable as those games is stupid; but I think they also need more time between replays than recent open world games like BotW, ER, or Mario Odyssey have even been out, so of course people who have already done second or third playthroughs of them aren't having as much fun as they'd hoped.