As a team you constantly need to assess whether a dependency should be brought in or of a re-implementation is not better.
Sometimes, the re-implementation is so specific to you actual problem that maintenance becomes almost free. A generic solution always open more doors to problems and require more effort to maintain.
For a rich client web application, you need a really good reason not to bring an external dependency such as React.
As a team you constantly need to assess whether a dependency should be brought in or of a re-implementation is not better.
Sometimes, the re-implementation is so specific to you actual problem that maintenance becomes almost free. A generic solution always open more doors to problems and require more effort to maintain.
For a rich client web application, you need a really good reason not to bring an external dependency such as React.