The belief that humans have arrived at a plateau and no longer are subject to evolution is also evidence that you do not understand evolution.
I assure you, homo sapiens is under great evolutionary pressure to evolve an effective response to birth control.
It is also worth noting that it is suspected that our large brains mostly reached their present size to enable us to be more effective in interacting with each other. As long as we would prefer to not wind up alone on Saturday night, we'll be under pressure to better figure out how to get other humans to do what we want them to do. There is no upper limit to how much intelligence could be brought to bear on that problem.
(Though in practice I believe that we'll build machines smarter than us, which will improve far more rapidly than we could ever hope to.)
So, your counterargument is that birth control and Saturday Night Fever will have a bigger effect on the evolutionary process than enabling people with congenital diseases to reproduce, and that, moreover, this will somehow continue to produce increases in intelligence at the same rate as we experienced going from ape to human?
I'm not claiming evolution is finished. I'm claiming it is affected and I don't see compelling pressure to select for ever-greater intelligence. Even if I found your argument compelling, you're hardly talking about the same kind of intelligence as the GP. Intelligence is one of those squishy things that resists good formal definition.
I am not trying to predict the future. I am merely saying that evolution isn't done, and the presence of medicine and a high quality of life doesn't change the basic equation of "survival of the fittest".
And intelligence is selected for for reasons that are not addressed by modern medicine.
I assure you, homo sapiens is under great evolutionary pressure to evolve an effective response to birth control.
It is also worth noting that it is suspected that our large brains mostly reached their present size to enable us to be more effective in interacting with each other. As long as we would prefer to not wind up alone on Saturday night, we'll be under pressure to better figure out how to get other humans to do what we want them to do. There is no upper limit to how much intelligence could be brought to bear on that problem.
(Though in practice I believe that we'll build machines smarter than us, which will improve far more rapidly than we could ever hope to.)