Every newborn has between 50-70 de novo mutations in his genome, mainly depending on the age of the father at conception.

2% of the human genome coding dna, but the total portion of the genome wich is subject to purifying selection is something like 5-10% of the total.

It follows that around 5-10% of those new mutation per newborn human have an effect on fitness, with the vast majority of them being deleterious (even if many of those very lightly so i. e. being a redhead or mild myopia).

Now, to maintain fitness in a population every deleterious mutation must be eventually eliminate from the gene pool through the disadvantage in fitness that its carriers have.
But I don't see how a species with such high intergenerational time and that produces quite a limited number of offspring could ever do so. 5% of 50 gives us 2.5 deleterious mutation per newborn. An unreasonably high percentage of people should fail to reproduce and women should have tons of kids for fitness not to decrease.
I read a paper by Michael Lynch that calculated at 5% the per generation loss of fitness of humans due to de novo mutations (I will post it if I find it).That's a lot.
Am I missing something in all of this?