I played piano for some 10+ years and never had heard of Gaspard de la Nuit or really knew who Ravel was, I had heard his Bolero but that was about all! Chopin and Liszt Etudes I became aware of around 6-7 years into my piano journey and started to dabble with in my teenage years a few years later when I finally accessed the sheet music and some more recordings. Beethoven Sonata's I knew very early on as a child since we had cassette tapes of them which I loved, this inspired me to learn his Sonata's when I was younger.
The way you put it, there is an advantage to this. How would you get to know lesser known composers? I'm personally not so sure that it's healthy to only know about Beethoven, Chopin, etc., if I'm getting you correctly.
For a long time before the internet the piano world was full of mystery and discoveries to be made. Today you can listen to all the popular masterpieces in a matter of weeks, something that to me was revealed over many years. This to me seems like a problem, it's just so overwhelming for people who are developing at the piano. I felt overwhelmed as a teen seeing all these new works on the internet even though I had over a decade experience behind me and a teacher to support me.
I definitely agree with the sentiment here. Of course, I would literally not be playing the piano if not for the internet, so I am deeply indebted to it. However, I think in general, that the deluge of information the internet provides overwhelms most people and often, paradoxically, makes them somewhat dumber. The amount of information seems so insurmountable that many people end up not spending enough time thinking about anything, and it leads to a shallow, uncertain understanding of most things. Another problem is that it's unmoderated, and people who aren't good at critical thinking just don't know what to believe any more, which I believe leads to more delusional thinking.
I come across many self taught pianists who are just thinly spread all over the place and with plenty of holes in their development because they have so much listening experience and have developed a taste of music that is quite advanced. It is just so backwards I feel, there should be years of not even knowing about these master pieces while you study the piano and then when it is finally revealed to you it becomes a new chapter in your journey a new target.
I feel personally attacked

I see where you're coming from, but if you think of music as being a language, wouldn't it be best to have as much listening exposure as possible? You had classical music in your home growing up, which is certainly one way to go about it, but I think that making it a point to actively listen to a lot of music is important if you have had no prior exposure. For example, I did not have any exposure to classical music growing up, except the occasional Tom and Jerry cartoon. So there's no conceivable way in which I could make musical decisions while playing without getting some first-hand listening experience.
However, I definitely agree that the listening should be deep rather than shallow, spending a lot of time on individual pieces and figuring them out.
When I was younger the piano students rarely overextended with works too difficult for themselves it just didn't happen, the choice was made always by the teacher and we followed. Nowadays students are expected to have some freedom of choice as to what they play and teachers should submit to it, we have the internet with access to so much music that we can craft different musical paths which are still highly effective to develop with. Self learners however easily have access to sheet music of pieces far too difficult for themselves and then go ahead and learn it.
I think this is somewhat true, but not quite. I think that the average student is much more likely to overextend themselves nowadays. However, I think that the obsessed types overextended themselves in the past as well. Ted, for example, often recounts the time he taught himself the Fantaisie Impromptu before he met his first teacher, and this was about 60 years ago.
but it is very expensive with your time wasted and sets people up for a world of estimated piano playing which is just such a tangled mess to unwind that it is almost always better to build from bottom up instead.
Yes, this has happened to me. Now that I've got a really good teacher, I have realized what people were telling me about estimated playing. However, there are multiple obstacles. I wouldn't entrust my progress to 99% of the teachers out there, and it's very likely that my teachers would have been like that starting out, discouraging questions and stifling creativity -- and that would have put me off piano playing for a long time.
So I'm somewhat glad that I taught myself to the point where I could tell what I actually needed in a teacher, and to where I've gotten some confidence in my abilities.
However, again, the way I've seen so many teachers teach online, on YouTube, on pianoworld and pianostreet, really scared me off. I was concerned that I would be made to blindly do exercises and recite things with no true understanding like I see so often.
I have observed that the regular posters here, like yourself, are excellent teachers and pianists, but from what I've seen, the horror stories are considerably more common.