This is the first time I've seen Flask being called crappy. Do you mind elaborate why?

Flask isn't crappy. It's an excellent way for learners & aspiring polyglots (like me) to build a functional app and learn about routing. And it's got a bazillion useful extensions.

Is it great for a production environment? No clue. Same with Tornado. But it's definitely a solid pick.

>does anyone even use Tornado anymore?

We do for as many apps as possible. The async / callback structure is far easier for our developers to understand over Javascript/Node. Tornado is significantly different from other Python frameworks like Django and Flask, but IMHO it is under appreciated.