There have been two things going on.
The genius-type was an Endogenous personality^ - which I have defined as both highly intelligent and inner-directed, inner-evaluated, inner-motivated (in other words, with some aspects of the Psychoticism trait as described by HJ Eysenck).
Intelligence has declined a lot, so there aren't many people nowadays with the extremely high intelligence which was characteristic of geniuses 150-200 years ago. I think that the decline has been considerably more than one, and perhaps two standard deviations or (very approximately) 20-30 modern IQ points.
In practice, this lower average intelligence means lower peak intelligence, which implies that the modern genius would be less of a genius than in the past - this can be seen in both the arts and sciences.
But the modern genius and the social selection mechanisms have also changed so as to exclude the
genius personality type.
This is due to factors both deliberate and accidental. Deliberate, because the Endogenous personality was usually a man of European descent; and inadvertent because of trends such as increasing the length of formal education, increasing the required number of educational certifications, allowing more cheating in educational evaluations; and more committee decisions regulating the workplace, more and more-complex bureaucracy, and the expansion of the public sector with domination of the state.
So, what has replaced the genius of yore? At best, we still have geniuses, but just on a smaller scale.
More often we have people who among the most intelligent of the population, but externally-directed, socially-orientated and using established evaluative criteria - in sum, people who are utterly lacking in real creativity, but clever enough to fake it by extrapolation, selection and recombination. Thus we get fashions rather than breakthroughs.
Mixed-in are a few charming psychopaths, who may be intelligent or not - but they are out-for-themselves, and have too short an attention span ever to achieve anything original
So that is what we now have instead of geniuses, to replace geniuses: careerist drones and plausible con-men.