It is a sorry fact that Classical music has seen its heyday come and go, and I would like to try and outline a few reasons why this occurred
In the 19th century, concert recitals became quite popular due to folks such as Liszt, Thalberg, and other composer-pianists. Normally, composers would merely perform their own works in concert, either at a premiere, or in subsequent performances. Liszt, however, really pioneered the piano recital, in which he would perform not only his own works, but also those of other composers (Beethoven, Chopin, etc). This, as its popularity increased throughout time, gave rise to the structure of modern recitals and performances that we know today.
Now, for a thought experiment. Imagine what would happen if there were around, say, 150 "pop" songs that were regularly performed. That is, artists have stopped creating their own music, and instead do covers of these 150 songs. Now, imagine that these artists were bound by a score, a score which they cannot deviate from, that is to say, they have to sound exactly like the original song. Would pop music not become stagnant and stale? It is for this reason that classical music has lost its mass appeal: artists are (1) not composing anymore (partly because, with the advent of the "recital", they can just perform other people's works), which leads to (2) the same pieces are performed over and over again, and (3) the score of these pieces is sacred, that is to say, it is blasphemous for an artist to tamper with the directions which the composer set forth. In other words, classical music has become stagnant and stale; there is little originality because there can be no originality given the framework which musicians must work under.
What, then, must we do? First, we must to some extent do away with the notion that the score cannot be deviated from. New criteria must be established to judge a "good" performance, for, according to some, a good performance can only be as such if the artist sticks closely with the score. We need more artists like Glenn Gould, who was not afraid to tamper with the score in favour of artistic expression and original interpretation. A good example is his recording of the first movement of Mozart's Sonata in A Major. It is a theme and variations, and, in the score the second to last variation is marked "adagio". Gould, however, plays it like an "allegretto". Lo and behold, it works, it doesn't sound "bad", and even fixes the architecture of the movement: the theme is slow, and, as the movement progresses, the speed and energy picks up, instead of being interrupted by an adagio in the second to last variation. What is needed is strikingly original interpretations such as this: artists must not be afraid to counter the composers intentions. If pop artists did covers which sounded exactly like the original they would not be terribly interesting; similarly, one can only hear so many renditions of Schubert or Chopin which sound robotic because they all follow the letter of the score.