Eugenics

[tame_deuces]

The biggest problem is that it is

1.) Extremely oppressive.

But ok, you said we should disregard that. The remaining problems are:

2.) It is illogical. It is based on assumptions that are at best misguided.
3.) It is impractical. Because enforcing it means totalitarity, which has a tendency to both fail spectacularly and be very expensive.
4.) It has severe implications. Eugenics in the past has led to some fairly bad political practices and some pretty stupid beliefs.
5.) It is biased. Eugenics is usually not a result of some sound scientific insight but more a confirmation of some naive prejudice.
6.) It doesn't solve the problem it pretends to solve. You still end up with someone deciding who gets to reproduce based on partially subjective criteria.
7.) It makes hazy assumptions. Eugenics assumes that the answer to a rather complex problem lies in only one place.
8.) It isn't realistic. Eugenics even if we assumed it had no flaws would only work in an completely idealistic setting.

It is most ways like the 'benevolent dictator' idea. Intellectual dung which someone with severe bias tries to make look good.