You are wrong. Those we are talking about (including myself by and large) also don't want to be told before the fight by someone else. Not sure why this is such a hard concept for you. If you want to go in blind, you don't want to stop and be explained the fight either.
But if you do run across someone who doesn't know the fight but does want some advice and asks, give it to them, it only takes a minute even for complicate fights. And then dive in.
If for whatever reason you are unwilling to do so, please just leave. Save yourself and them the frustration. Better yet, don't join the party in the first place, and avoid DF since you cannot guarantee who you will get. (And no amount of complaining on forums is going to change this)
Why have you ever been in a learning party if you don't approve of them?
It really doesn't. You can easily explain Ultima in about 1 minute. If you can't, you probably are over-complicating it for someone who is new anyway and they won't remember anything important. The extremes, also fairly easy to explain, though harder to do (though once you get them down they are in some ways easier than HM).
Not everyone started the game at the same time, or plays at the same pace, and they shouldn't be forced out of experiencing content because you think "it is lazy".
They should be able to learn in their preferred method, at their preferred pace, so long as others are also willing. (And there always are despite what your own personal experience may be).
It is pure laziness, to spend hours learning content through trial and error with other people who also want to learn it the same way? Really? I don't understand this mentality. In my mind it is pure laziness to have someone else hand feed you the solution to a puzzle so you don't have to spend time on it yourself. As I said. If you don't want to be part of such a group. Do Not Join. Problem solved. There is clearly a huge mindset difference. Honestly. They don't want you anymore then you want them. Different play styles. Neither should be forcing themselves on the other.
I have more than one character at endgame. I choose to leave the one I never touch as my face on the forum because it was my first not because it is my "main". Not that it is relevant.