It seems to me that you are talking about two things: a possible end goal of evolution, and/or whether a greater degree of happiness would be attainable or even desirable.

To the first I think there is some process which fairly begs to be played out. When I see the struggle to survive, the "life instinct", I think there is some determination to "be" or to "become" there. Beyond that I have nothing.

To the second question I think yeah, we could vastly improve our psychology and brain chemistry. We have lots of imbalances and primitive reactions that don't serve us well and increase suffering for everyone.

I read someone describe their experience of heroin as a complete absence of fear. Not fear of anything specific; the low level fear that is always humming away in the background in your brain and nervous system.

To relax that a little is profound (apparently).

I too think we need all the emotions; to be happy all the time would create an imbalance.

But if we could engineer ourselves to be a little less paranoid, that has potential to be an evolutionary advancement.