Yeah, stable economic growth and political stability? Who the hell would want that?
Political stability? Smith's Rhodesia was viable only so long as the territories bordering it remained colonial regimes. The regime itself was not viable, it depended on repressing the vast majority of the population and lacked the means to do so once that population got some outside help - in depended on others policing its borders. In fact that was the secret behind the quick european conquest of Africa: with the continent split after the Berlin Conference and each european power (the only industrial powers) agreeing not to hinder the others, the lack of local industry and modern weapons made the whole continent an easy prey. The tho other industrial powers outside this arrangement were busy playing with their own empires, one in the Caribbean and Pacific (killing filipinos, etc.), another across Asia and eying China.
Once that short imperial age ended, after WW2, the domino of independence and war started in Africa and could not be contained - the new world powers were interested in making changes and didn't care about the means. It was fitting: live by the sword, die by the sword - a new imperialism ended the old.
Smith was a racist, he used terrorism against the black population that dared rebel, and he was crazy to believe his petty state could endure independent in what was being used as an arena for the fight between the two world superpowers (plus the chinese and a few others). Well, sane enough in the end to step down, do at least there he was better that Mugabe, I'll grant that. I don't see any scenario where unstable regimes, regimes which oppressed most of the population, could endure in Africa. There were too many outside parties interested in destroying them, fighting
to the last african if necessary. So even if your argument that "all things considered the black population would be better off" was not false (and I believe it is) - power grabs by white minorities inevitably led to wars which those white minorities could not win - and leave a legacy millions of dead and displaced and new civil wars. So most of Africa was and is screwed, barring a near miracle. I won't just put the blame on people like Ian Smith, or like Mugabe.
Most of the blame rests closer to some major world capitals. Africans still lack the unity and the material conditions to resist foreign manipulation of their affairs, and so they'll continue to be used as pawns. Ian Smith was just a mediocre puppeteer who retired when he understood he was too weak to keep playing that game. Rhodesia was actually lucky in that it was so isolated and unimportant that it escaped being turned into a battleground during the 1970s and 1980s.