If you agree that being challenged and improving have a causal relationship, then perhaps it would follow that random parties would not remain such a burden forever.
Given how many terrible players I see at max level, still flubbing mechanics that should be nothing new at this point... I'm more skeptical of that happening than you are, I guess.

A remarkable amount of the "progress" made by players as a whole in this game has come solely through the efforts of other people who actually knew what they were doing. How many people do you see in, say, the Steps of Faith trial nowadays, who have clearly gotten past said trial before (often because no "new player" message shows up) yet they don't know how to do anything in the fight other than stay under Vishap and attack him?

Or did you mean that having to put in effort is tedious? I can't say I'll ever understand that point of view.
I gave a pretty good example of this with the Weeping City weekly, I think. Once a daily/weekly task becomes too much of a pain to do, I'll pretty much stop wanting to do it. I don't feel these sorts of things *should* be a pain to do.

I think most are fine with needing to put in effort to clear a savage raid or something, but once you start extending that to content designed for story progression or just gearing up so you can even *attempt* the savage raids... yes, it gets tedious. And I feel that's more likely to push people away from the game rather than "encourage" them.