It’s perfectly viable, but it’s seen as pretentious I guess. That’s a shame because I think it very useful for making a broad point on a touchy subject. People seem to be so ready to take offense at anything, it would be nice if one could say what one thought without having to add "this isn’t directed at you specifically, it’s a general ‘you’ ".
Or maybe I’m just a pretentious twit.
Another question is when did it become ok in the New York Times crossword puzzle for “one” to refer to a thing. “One that dries” for “towel”, and such. Eugene Maleiska would not have allowed that.
Well, sounding pretentious is certainly a part of it, but a phrase like “It would be nice if one could say what one thought,” pretty much guarantees a follow-up of “One what?”
Every. Single. Time.
Because it’s the loneliest number that you’ll ever do.
Although two can be as bad as one.
One is still perfectly crommulent and I use it all the time. I’m about as unpretentious as they come.
I have never seen anyone offended by such use of the word “one.”
“One does not simply change the use of pronouns overnight.”
For you Game of Thrones fans
It is true that using
It is true that using “one” is falling out of favor in formal writing. I teach English and can attest that several contemporary writing guides suggest avoiding it. Beginning and intermediate writers are often faced with rigid rules to help encourage style development. When penalized for using first-person, second-person, and gender specific pronouns, these writers often latch on to “one”, and then they overuse or misuse it. It can spoil good writing if overused or used awkwardly.
I find that I’m using it more frequently, but I suspect that that’d due to the influence of French and Esperanto, where the corresponding constructs are very frequent.
Yes, I remember from elementary French lessons, that the equivalent usage is quite standard.
Note also, Cecil uses “one” like this quite regularly.
I use it from time to time.
Yes, although the French “on” is derived from “homme” (“man”), while the usual word for “one” in French is “un/une”, so it doesn’t have the “one what?” problem as in English.
But that’s a minor problem. I agree, it would be nice if it got more use, if only because “you” (in practice, the much more common equivalent of French “on”) is even more ambiguous (you mean me?).
LOTR, actually.
“One does not simply walk into Mordor.”
I have never encountered this.
Of course, Eugene T. Maleska would also have spelled his name correctly.
As for the OP–I don’t know when you begin to see people moving away from “one.” Anecdotally, my father always spoke in what you might call high-academic-ese, both in and out of the college classroom (yes, he was a professor). To me as a teenager in the much-less-formal seventies it sounded impossibly stilted, formal, and, yes, pretentious. None of it sounded as pretentious as the constant use of “one” where most people I knew, even his colleagues, would’ve used “you.”
(Just so we’re all clear, my dad was in many, probably most, ways a great guy, even if his speech habits were hard to swallow at times.)
Anecdotally, then, we’re talking a process that is at least several decades old.
We lived in Paris for a few years when I was growing up. I learned to read and write in French and English at the same time (it’s amazing that I can spell anything, really!) which is where I get my partiality for “one”. I find I use it more in writing than in speaking, and if spoken it’s generally in a sardonic or sarcastic comment.
Here’s hoping the unpretentious one-users can brig it back into fashion! 
I found it very useful in French as it saved me having to conjugate the verb.
One uses it here when one can.
This is relatively easy to avoid. For example, what you are actually saying in you final sentence is that “it would be nice if I could say what I thought without having to add [a disclaimer].” Or possibly “it would be nice if everyone could say what they thought without having to add [a disclaimer].” Or even “it would be nice if people could say what they thought without having to add [a disclaimer].” All of these work fine.
Examples from a website explaining the use of “one”:
[ul]
[li]“One would think the airlines would have to close down.” Clearly a statement of what the speaker thinks, so easily replaced with “I.”[/li][li]“The young comedian was awful; one felt embarrased for him.” “I” would work here, too, but a better replacement would be “everyone.”[/li][li]“If one fails, then one must try harder next time.” “One” is actually horrible here, since it could refer to a number. While “you” would be the most natural replacement, since we are dealing with an aphorism, “someone/they” works well enough.[/li][/ul]
That website says that the replacement with “you” is an American thing. Is the use of “one” as an informal general pronoun that much more common in British or International English?
That was my sense; that Brits were more likely to use “one” than Americans.