I think you have to remember Joko that modern man is quite a lot removed from what we first were.Advances in technology, medicine, agriculture and everything have progressed at a staggeringly fast rate.
From an evolutionary point of view, a species is a success if the overall design allows the species to pass on its genes for the next generation. And given an estimated species population of around 7 billion and counting, humanity certainly does that.
Modern humanity, thanks to advances in, well everything really, now lives far longer than the original design might have envisioned. We also eat much, much more processed food and sugar than the original design specs specified, and sugar especially is a major contributor to tooth decay.
Finally - We are not designed to an idealised, perfect template.An examination of the design of the eye, or the prostate gland, or the meandering, looping path of the carotid artery will tell you that As a species, we are a compromise between differing, competing systems. For example, it may be that sharp vision was, from an evolutionary perspective, a more valuable asset and so resources were devoted to developing vision at the expense of teeth.