I feel like your post and my post are tangential to each other.

Having it cut off abruptly because of a mistake calculation on the DM’s part while prepping the session goes against the story.

As I said, if you don't want situations where a character meets an abrupt end anticlimactically, don't play games that do that. That's a pretty big property of DND and close relatives, but that's not how ttrpgs have to be. Or, if you don't want to throw out the baby with the bathwater, have some sort of table rule to handle it. I guess "hey GM can you fudge it if we're going to die stupidly?" would be a rule you could adopt, even. Informed consent is important.

I think it's because DND is so old. It's like a black and white tv, and people have all these tips and solutions to solve problems like "I can't tell if that's red or purple", and ignoring people saying "if that's important to you, get a color tv". Black and white is definitely a valid choice for media, but it probably shouldn't be the default.

Also, having a player sit around twiddling their thumbs for the rest of the session because their character died is not fun and goes against the reason why we play games in the first place.

This is also kind of a dnd-ism that can be solved in various ways. Fate's consequence system, for one example.

Fuck realism, it is a fantasy game we play to have fun. So getting rid of unfun aspects isn’t just recommended, it is a necessity.

I mean, I don't particularly disagree with this but my point wasn't really about "realism". It's about the social contract. I don't want a game where the GM is telling a fixed story, and will move the pieces around to keep it on track.

Like, in one game the party was trying to deal with a wyvern that was making trouble in the region. The players had several misfortunes that I could have fudged, but it wouldn't have been better

They wanted to use some spell or other to keep it from flying away. I rolled the save in the open. It saved, and flew away. Yeah, I could've just lied and said it failed, but why even have a saving throw system if you want that? Other games have meta game currency to force issues one way or another. Play that. Or port that into DND.

They tried to poison the wyvern. Rolled in the open to see if the wyvern ate the bait, or spotted the players hiding nearby. It rolled well, and took off before eating a full dose. Could've just fudged it, but they knew the odds.

So they followed it to its lair, dealt with the kobold cult (they made friends because this group was great), and had a climactic fight with the wyvern on top of the plateau, by the lake. Including a dramatic "wait if I dive into the water I take less fire damage, raw? I'm a warlock of the deep I'm diving in!" moment.

Or the time they challenged an NPC group to a battle of the bands to see who would claim ownership of the macguffin. The players lost. The NPCs took the macguffin back to the university. But they negotiated a compromise to borrow a similar, weaker, tool, and went on with that. The story was different, but it wasn't worse. Fudging the rolls to be like "oh wow guys they really borked it up" would've felt cheesy as hell.

So yeah, I could've fudged it, but I didn't have to. I'm not writing a book with a fixed plot.

TTRPGs are games where you create stories, and sometimes those stories are "we did something we shouldn'ta, and someone got ganked". What you're describing is someone reading you a story book.