I’m not sure why it’s even hard to imagine a centaur (especially the medium sized centaurs of 5e) climbing things.
A centaur can pick things up off the floor, and horseshoes with divets in them to facilitate getting a grip on things is hardly something that would require hyper advanced technology.
Y’all really can imagine the creature existing, can easily imagine a bullett existing, and rocs, which aren’t magical creatures but are bigger than the biggest flying creatures that have ever existed IRL and fly as easily as a hawk, but a centaur being a bit more agile and bendy than a horse, with horseshoes that it possible to get purchase on the round rung of a rope ladder and in nooks and crannies in a rock face, is just beyond the pale!?
Like...what?
And like...what’s up with the boats!? You think a centaur couldn’t be a sailor, really!?
Guys. The non-magical parts of D&D are not realistic. They’re comic-book “believable”, at most.
It reminds me of having to show gymnastics completion and free running exhibition videos to a DM friend because he was convinced that his players were trying to do impossible stuff with their acrobatic characters.
Here’s my reasoning, for what it’s worth. I’m fine with magic existing and with magical creatures existing. It’s a fantasy-adventure game. But, once I accept that those things exist, they have to follow the same kind of internal logic as the rest of the world and its inhabitants. Things need to eat, sleep, and naughty word...unless they don’t. Unless the MM or adventure or fairy tale I’m pulling a creature from gives me details on the thing, I’ll make them up with an eye for verisimilitude. You shove a manticore in a dungeon room but it can’t fit through the door...okay, so it was either teleported in or it came in when it was small enough to fit. Either way, it still needs to eat, sleep, and naughty word. Even if it never comes up in game, these things need to make sense.
The more “it’s magic” answers you give the less believable it becomes and the less interested I am in playing or running it. That last part is clearly a preference. Some people don’t care about those details. I do. Even if there’s magic, I still want the world to make internally consistent logical sense. Even if it’s only in the loosest sense of those words. Once I accept that the fantasy is “real” in terms of the fantasy world, then it has to move, act, behave, respond, etc as if it were real. Physics effects these fantasy creatures unless there’s magic involved.
A centaur climbing a ladder. I’ve never seen or read of a centaur bending forwards or backwards at the “join.” So, to me, that bit is either completely inflexible or mostly inflexible. So they’d have to climb the ladder with their hands and arms and the front set of legs and hooves...leaving the rest of their body hanging in air. I’m going to say that there’s more weight behind that line of arms-hands-front legs-hooves than there is on that line. So, physics takes over and they fall.
Likewise, a centaur isn’t going to be able to pick a lock with its hooves. They can pick a lock with their hands or kick the door in with their hooves. But there’s no dexterity or fine manipulation with their hooves. Internal consistency. They’re hooves, not feet or fingers. No digits, no fine manipulation...without magic. But I guess that makes me a naughty word DM to a few people here. Oh well.
So it comes down to how does the physical mechanics of a centaur work? A horse‘s neck is fairly flexible and they can lower their heads to the ground. And a person can bend at the waist to touch the ground. So is the torso spine a horse’s neck or a human spine? That difference matters.
Stand up, lean forward by just moving your spine, not your hips. How far can you get? You can hunch forward and reach a few inches closer to the ground. But you’re not touching the ground without moving your hips or bending your knees. I don’t see “hips” where the “join” is in any centaur art. So I think that bit of anatomy is fairly inflexible, like the human spine. Without that flexibility, without hips or working like a horse neck, it would be impossible to climb a ladder. The shape of a centaur is basically an inflexible “L”. You need that weight roughly in a line to not fall off a ladder.
This has been “fun”. Merry, happy, festive, joyous, etc.