I think that one issue is that the top ~200 mathematicians are of such high intellectual caliber that they’ve plucked all of the low hanging fruit and that as a result mathematicians outside of that group have a really hard time doing research that’s both interesting and original.
Your standards seem unusually high. I can cite several highly interesting and original work by mathematicians who would most probably not be in your, or any top ~200 list. For example,
Recursively enumerable sets of polynomials over a finite field are Diophantine by Jeroen Demeyer, Inventiones mathematicae, December 2007, Volume 170, Issue 3, pp 655-670
Maximal arcs in Desarguesian planes of odd order do not exist by S. Ball, A. Blokhuis and F. Mazzocca, Combinatorica, 17 (1997) 31--41.
The blocking number of an affine space by A. Brouwer and A. Schrijver, JCT (A), 24 (1978) 251-253.
I would like to know more about the perspective you claim to have gained which makes you think this particular way.
How do you make a priori judgments on who the best mathematicians are going to be? In your opinion, what qualities/achievements would put someone in the group of best mathematicians?
How different would your deductions be if you were living in a different time period? How much does that depend on the areas in mathematics that you are considering in that reasoning?