I think there are two things going on here, that explain satisfactory why we feel like we see fewer geniuses now:
1) There are now so many people who would be seen as geniuses 150 years ago that they drown each other out, leaving little space in the spotlight for someone to gain the culture defining attention a genius in 1850 might have gotten.
2) In addition, the culture that would be defined by such a genius is now several orders of magnitude more complex than it was in 1850. That means getting everyone to agree on anything is a much harder feat now, much less to get the zeitgeist to agree someone is a genius. (Just look at people like Gates, Jobs and Musk - just as quickly as they are seen as geniuses by one part of the culture, another part wants to drag them down again).
1) There are now so many people who would be seen as geniuses 150 years ago that they drown each other out, leaving little space in the spotlight for someone to gain the culture defining attention a genius in 1850 might have gotten.
2) In addition, the culture that would be defined by such a genius is now several orders of magnitude more complex than it was in 1850. That means getting everyone to agree on anything is a much harder feat now, much less to get the zeitgeist to agree someone is a genius. (Just look at people like Gates, Jobs and Musk - just as quickly as they are seen as geniuses by one part of the culture, another part wants to drag them down again).