[adrianhel]

Just use vanilla JS to begin with. If your app has a lot of interaction, you can use React with create-react-app makes things easier.

You can still use vanilla JS, HTML and CSS. And it's not morally wrong.

Assess the requirements. Lots of moving parts and not a whole lot of time? React or Vue lets you draw the big lines quite simply. Need something simple or with fancy animations? Vanilla may be your best bet.

Personally I use vanilla for simpler stuff and React for more complex apps.

Don't worry, just make cool stuff. Nobody ever cares how you built it, just that it works.

Trello still uses CoffeeScript. It really does not matter as long as it works.

PS: You can combine if and when needed.