Capitalism has had 400 to 500 years (arguably even longer), and in that time it oppressed, colonized, enslaved and engaged in genocide of hundreds of millions of people, thoroughly warped democracy (e.g. bribes and huge amounts of money spent to ensure the election of capitalist-friendly politicians), thoroughly warped geopolitical evolution (e.g. the propping up of dictators to ensure the flow of oil and other resources needed to keep the capitalist machine humming), and is thoroughly wreaking havoc on the environment as it demands we consume as much as it can produce, again to keep the machine humming.
Yet we've only experimented with socialism for 100 years (and that's being generous with the definition of socialism) and it is dismissed out of hand as a failed idea and that its supporters are crackpots.