React is a library. React has its own router, you don't need anything for forms...you can do forms in React like you can in any other webapp. But 3rd party tools are nice. You can use CSS animation in React without a need for tools, but those are also nice to have. CSS encapsulation can be solved by some creativity with CSS files, but this is a problem everywhere in web development. Tools like Styled-Components extensively solve this issue and is, once you learn the basics, pleasant to work with. Angular has a much steeper learning curve than React.

Also, Context hell only happens when developers have crappy standards and don't put any thought into what they should. This is a sin that is present in every facet of web development, including AngularJS. Context, callback, etc hell is what happens when a developer is in a hurry to meet deadlines and not pay any attention to quality of work. This is why this fast-moving industry needs to SLOW DOWN. We're shooting ourselves in the foot by rushing innovation.