... Everyone knows that communist central planning was a terrible failure. Do you think no else noticed?...
Obviously.
In other words, very, very few noticed. I just posted a glaring example, Crazy Bernie's total rent control.
What you don't seem to understand is that it doesn't start backwards, i.e., from the end (as a terrible failure). It takes a lot of time for people to realize it is a terrible failure. It starts nicely, with all those wonderful promises of a more just world, affordable or free this or that. It took 70 years for USSR to disintegrate (and even that took a lot of outside pressure). It took Venezuela 10 years to become a basket case, after people voted for socialism. The US still has strong checks and balances, so it will take years for the loonie left to dismantle it into a socialist "paradise." But it will happen, eventually, if people do not wake up and notice, as you said, that socialism* is one giant and terrible failure.
* But, of course, in your view, it is a brand new version of socialism, which, this time, is going to finally work
P.S. There is nothing really new in what the "new" "democratic" socialism proposes. All old news. Free health care? Free education? Free housing? Check. Check. And check. All existed in the USSR and other socialist countries.