com addins are only for legacy office applications. Also they are only supported for the desktop windows versions. Though I would not be surprised if even this support is dropped.
The Office team supplies react components for all the office style controls, and matching css for office look. If you pick another framework besides react, they have a standalone sass/css package. The office team tends to use react for the official plug-ins so they are a good choice. You just need node installed to develop.
React fabric ui (sample code builds task pane)
Fabric ui sass
Not sure why you would invest time learning an obsolete technology. The time it takes to learn to write a simple com component (office add-ins require discovery also be coded), you could probably code the complete plug-in modern style.