I will keep using "classic" for as long as possible. This trend to turn everything into painfully slow web apps is really getting on my nerves. As an example, I use quick steps very frequently to categorize emails. In classic Outlook, I click the button and the email is moved immediately - in the new Outlook it has a ~1 second delay until the email is moved and I can move the next one. Takes so long to get through my inbox.
I discovered that setting after building a new desktop PC recently. It was disappointing to find the awful keyboard lag introduced by the new OS, as I use MS Office daily.
About start menu animations, I actually prefer the UX without them. I press the Win key and the menu appears, no need to wait.