When people bring up BOTW's rain, it seems to only be discussed in terms of folks not liking that it impairs your climbing. And to an extent, I do empathize, and I think it might've helped if, for example, the climbing gear or some other item let you climb unaffected by it.

But I feel like there's so much more to it that just that.

For one thing, it actually is possible to climb in the rain; you just have to time your jumps right. It consumes a lot of stamina but it can be done. In addition, Revali's Gale bypasses this altogether, so in a way it does kind of act like an item that cancels out the slippage effect.

The game even has a weather forecast icon in the HUD, so as long as you pay attention, it shouldn't catch you out.

Rain does a lot more than just create slippery cliffs though; it drowns out the sound of your footsteps and reduces enemy vision, making stealth more potent. It buffs electrical weapons, as hitting a wet enemy with one will not only do more damage but also create a lightning AOE. On the flipside, bomb arrows are extinguished, not just for you but also for enemies. It creates puddles, which offer up opportunities for both electrocution and using Cryonis.  Different animals come out during the rain.

I know it gets a lot of hate, but I personally felt like it really helped make the world feel dynamic and alive, and changed things up by making the player adapt. It's like if you were on a real adventure; you can't control the weather, you have to plan in accordance with it.

Heck, even before I found out about the trick to climbing in the wet or obtained Revali’s Gale, just finding somewhere dry to start a cosy fire and wait out a downpour felt like something you’d actually do on a journey out in the wilderness. It reminded me of going camping and hiking in the bush when I was a kid, and made me feel more immersed in the game’s world.

On the whole, I feel like it's somewhat underappreciated as its too often dismissed as just "it's dumb cos it stops you climbing".

The real problem with elements like that is, while interesting at first, in the eyes of some, they eventually become an annoyance that gets in the way of what they are trying to accomplish. That's part of what makes mods so valuable to the long term viability of a game. It's also why game developers need to get over this "play the game the way we intended" bullshit and learn to provide options. People like and dislike a vast array of features and settings. What one person loves, another might hate. Allowing people to tailor their experience is a consumer friendly solution.

Well, like I say, ideally the climbing gear or some kind of gloves would've allowed that, but Revali's Gale pretty much does.

You can also climb even when its wet; IIRC (haven't had to use it since getting Revali's Gale in March 2017) you jump after every 3 handholds. You burn through stamina faster but it's not like rain means you have to just give up.

All it does for me is force me to find a dry spot to sleep or literally wait for it to stop raining.

In that case, your solution is Revali's Gale. 

That's not always available, though, and the cooldown can be even longer than waiting on the weather.

True, but it's availability it up to the player. If I know I'll be needing it shortly, I won't use it all up. It can be upgraded to greatly reduce cooldown times as well.

Plus I don't think there is anywhere save the towers with only a single scaling route; if it's raining and the distance is too great to use the step-step-step-jump trick, I'll scout around the base and there's almost always an easier way up, and even a depleted Revali's Gale will recharge in the meantime.

I care not at all about a game being considered art.  I care that I enjoy myself while playing.

As an example, Fallout 4 has two upper difficulties:  Very Hard, which simply makes everyone, including your character, into bullet sponges; and Survival, which increases the lethality of attacks greatly, which I really like, but also includes a lot of other game-play changes, like restricting saves to when you sleep, which I hate.  What did I do?  I downloaded a mod that allowed me to play on Very Hard but with the lethality of Survival, which I enjoyed a lot more than either mode as they were programmed by the developers.  Enjoyment, to me, is what gaming should be about.

And, at the of the day, the option to change the gameplay also includes the option not to change the gameplay.

Realism should never get into the way of playability, especially if it's inconsistent. All I can say is that rain was the No1 factor why I stopped playing the game and that is just terrible game design. Sadly, the word "optional" doesn't exist in Nintendo's vocabulary.

"Here, have a gigantic world to explore with an all powerful and immortal protagonist who can wield magic and climb mountains for days without eating or sleeping. Oh BTW, that all powerful protagonist can't climb things that are slightly wet. Also, all weapons are made out of paper. Have fun!"

It breaks the flow of the game, regardless. The first few times, it gave a "Wow, this is neat" vibe, but beyond that I was just annoyed that my progress was constantly hindered. And you shouldn't have to resort to broken mechanics like the 3xstep-jump to get around a roadblock to the game. I would have much preferred an item or food combination in game that strengthened my grip to climb in the rain.