youtube is not a tool - it's a platform, and increasingly more hostile towards content creators (and increasingly biased towards commercial content or clickbait content). Twitch is same as youtube basically, but slightly more content creator friendly.

Unity, scratch, blender, these are all programming related. They are not beginner friendly at all.

itch.io isn't a tool either, but a website for distributing. The content you find on there are good, but most are not made with something easy like the flash animations would've been. Game maker comes close, but it isn't well suited for animation.

There isn't, and hasn't been, a replacement for flash animation suite, which is such a great, easy to use, integrated tool of drawing, animation and timing with a relatively simple scripting model. Even amateurs are able to make interesting animations with it. I bet you can't say the same for any of the tools named above.