Human Race's De Evolution

The human race is realy going down the shit hole. To thrive as a fucking race we usualy breed with only the fittest to survive. Yet we all produce mentaly retarded kids and people with severe disabilities and inadequet mutations in out DNA which will be passed on to there kids.

Eventualy all that shit will spread (slowley but it'll still happen) So what does that mean? Evolution doesn't apply to humans? Genetic engineering plox?

Am i wrong? Please tell me i am because if my theory is wrong then we're all doomed for a very slow and bloody death as a society.