Ascending isn't particularly difficult, it's just that it requires levels of attention to detail and preparation that verge on tedium for some.
One example: in order to pass through the Elemental Plane of Water on the Astral, you need to find the (moving!) portal. In order to do this with optimal safety, you want to have:
genocided all sea monsters, so you don't need to worry about krakens and the like
have a means of magical breathing, in case you do end up in the water
rustproofed all your metal armor and other gear
have a large stash of Scrolls of Gold Detection, in a Bag of Holding (itself blessed and stored inside and oilskin sack so that water doesn't get in and erase your scrolls)
have a means of safely giving yourself the Confused status
(reading scrolls of Gold Detection while Confused lets you detect magic portals)
a means of swiftly removing said Confusion, so that you can...
*use your Boots of Speed (or other speed-boosting effect) to close rapidly on the moving portal.
And that's ONE challenge on ONE level (although its deep in the endgame and considered one of the harder things in the game). Now imagine doing that for 100+ levels of gameplay... you CAN virtually guarantee a win in Nethack, but its never fast.
I spent a couple years playing hard in college. I read spoilers, and save-scummed for a while, then stopped save-scumming because it wasn't fun and I didn't need to anymore. I've lost track of my legitimate ascensions - at least one with every class, and then I started in on conducts and score maximization.
Now, I still play on and off for a week here or a week there. I can ascend about 1 in 4 times with the easy starting classes like Valkyrie. My YASDs inevitably come from rushing or not thinking things through, plus very occasionally getting screwed early by the RNG.
And I'm not particularly good at the game. Really good players can virtually ascend at will, with the only limitation being their available time.
I think what's not obvious to people casually familiar with Nethack is that success is hugely bound to memorizing spoilers (the NH community term for any non-obvious peculiarity of the game).
In the early game that means knowing what the various meaningless messages mean ("You have a strange feeling for a moment, then it passes"), knowing how to identify items from context (cost, weight, results of innocuous actions) and so on. In the late game it means knowing all the harmful stuff coming up and what counteracts it, knowing all the statuses and interactions (Gold Detection while confused, etc).
That kind of stuff is what wound up driving me from the game - anything past the early stages just felt like bookkeeping.
For me, reading the source code was part of what made the game fun. It was a sort of metagame, learning how to cast "real-world" spells by studying the arcane tomes that held the secrets of the universe. It by no means made me invincible (my death/ascension ratio was still topheavy) or even cut out the mystery; it just moved some of the action and exploration from the game screen to a text editor. Two games in one.
Every 5-10 years I end up losing a couple days to NetHack. I'm overdue.
I've been a NetHack player since about 1990, and have ascended every class at least once, and I agree with you about the tediousness.
One roguelike I'm really enjoying these days is Dungeon Crawl Stone Soup. It's very much like Nethack in many ways, but the developers have made it a conscious priority to remove all of the tedious elements or the need for spoilers. They have been mostly successful with this, IMO.
Your example is a bit exaggerated, though I agree with you directionally. There aren't quite 100+ levels (more like 50-60 including the Mines and the Quest), and you don't have to do all those things: I rarely genocide sea monsters; my magical breathing is usually just a ring of levitation, which you need in other parts; you can easily get by without rustproofing your armor; the means of removing confusion and the speed boots are both things that you want/need earlier in the game too (vs a special preparation just for the Planes).
Once you've beaten it a few times and have a generally strong command on all the game mechanics and interactions, I think the fun part tends to be figuring out just which things are really necessary and which aren't, and generally optimizing your plan along some dimension or another (conducts, time, minimizing tedium, going for a streak, etc).
One example: in order to pass through the Elemental Plane of Water on the Astral, you need to find the (moving!) portal. In order to do this with optimal safety, you want to have: genocided all sea monsters, so you don't need to worry about krakens and the like have a means of magical breathing, in case you do end up in the water rustproofed all your metal armor and other gear have a large stash of Scrolls of Gold Detection, in a Bag of Holding (itself blessed and stored inside and oilskin sack so that water doesn't get in and erase your scrolls) have a means of safely giving yourself the Confused status (reading scrolls of Gold Detection while Confused lets you detect magic portals) a means of swiftly removing said Confusion, so that you can... *use your Boots of Speed (or other speed-boosting effect) to close rapidly on the moving portal.
And that's ONE challenge on ONE level (although its deep in the endgame and considered one of the harder things in the game). Now imagine doing that for 100+ levels of gameplay... you CAN virtually guarantee a win in Nethack, but its never fast.
I spent a couple years playing hard in college. I read spoilers, and save-scummed for a while, then stopped save-scumming because it wasn't fun and I didn't need to anymore. I've lost track of my legitimate ascensions - at least one with every class, and then I started in on conducts and score maximization.
Now, I still play on and off for a week here or a week there. I can ascend about 1 in 4 times with the easy starting classes like Valkyrie. My YASDs inevitably come from rushing or not thinking things through, plus very occasionally getting screwed early by the RNG.
And I'm not particularly good at the game. Really good players can virtually ascend at will, with the only limitation being their available time.