Unwillingness to accept? What evidence do you have that the 20th century was the inflection point in intellectual progress? We have many more brains with much more free time now, not to mention pocket supercomputers, the internet and AI assistance. I expect the pace of discover to increase if anything. Maybe you're just suffering from your perspective of being alive right now, like all those kids on youtube who say past music was so good, because they see a highly filtered and compressed version of the past.