I entirely disagree! I do think it's you who are being selfish in this instance. What right do you have to block others on an escalator?
You seem to be talking about one escalator in one location. You forget that in a large shopping mall in Bangkok like Central Chidlom there are 6 escalators all but linked and that some people take all 6 to get to the ground floor. So the total time saved by walking down is a great deal more than just a few seconds! And in Moscow and St. Petersburg, some of the escalators are amongst the longest in the world with again a much greater time saving. I'll be interested to know if you also stand like that on the moving walkways at airports? I landed at BKK a week ago and my flight parked at the furthest gate from immigration. I believe it took 8 moving walkways to cover that distance. In an airport, my priority is similar to that of most - get to Immigration fast to avoid longer queues. So when a mob of people block a walkway, I loudly say "Excuse me!" and that will usually open up an empty space. Do you just stand there on the walkways at airports?
In Hong Kong, Taiwan and Japan there is a much greater understanding that one side is for those who just wish to stand and the other is for those who wish to walk. To me that is absolutely sensible and I believe (although I have no proof) that this has to get more people to the end of the escalator/walkway more quickly which is surely what is needed, especially during a rush hour on the London underground. If it's free-for-all or everyone just stands, the London Underground tests just cannot have come to the conclusion that there is no such benefit. That makes zero sense.