look at lots of modern concertos. many are extremely difficult, like the 3 xenakis concertos. not all modern concertos are extremely difficult, but a good bit are.
the ligeti concerto was premiered by aimard i believe. this is definitely a horrendously difficult piano concerto. seeing the score pretty much confirmed my idea of its difficulty.
according to da Pareto principle
80% ov da people iz idiotz, dere exiztence haz no apparent impact of da world or human civilization itzelf, and da othah 20% makez up fo da zheeyeatnezz in da world
da overwhelming popularity ov da dongah provez nothing but dat he and hiz under-educated audience will go down in hiztory az oblivion