And I wouldn't say communism achieved worse outcomes. Countries adopting some form of communist ideology experienced some of the most rapid increases in industrialization, QoL, and education. They weren't perfect, but they definitely didn't drag everyone down to the previous minimum.
Most of the communist regimes people use as examples rose to power at a point in history when new technologies and industrialization were having a huge impact on the way people lived.
A mix of capitalism and socialism that made a point of educating and upskilling their population would have achieved the same goal without the brutal massacre of a chunk of their population.
Industrial technologies helped capitalist countries succeed just as much as communist ones but you attribute capitalist success to economics and communist success to the technology. Capitalism hardly uplifts, it sabotages the growth of previously colonized countries, extending imperial rule. Even in the countries on the benefiting side of that imperial relationship most of those benefits are going to owners and not workers. The exploited country could get most of the benefits with few of the downsides by just having an open trading relationship, but historically countries trying to achieve some level of self determination are met with a combination of military force, espionage, and embargos.
One of the big problems with communism is that economic prosperity is framed fundamentally as a zero sum game. When that's a foundational axiom of the system you build you wind up not building systems of growth, only of redistribution. It has rippling effects throughout the culture and the philosophy of a nation that attempts it.