> I don't understand why, with React, you need to install a 3rd-party dependency just to update your meta tags.

You don't. This seems to be a common misunderstanding. You're free to and should write your meta tags (and everything else inside the head tag) in plain React components. It's enough to do this on the server side, but the document title should be updated client side, too. React-helmet is an antipattern.

It's just images and videos, like InVision or other tools like that. Click button -> change / overlay an image or play a video.

This isn't a bunch of slides with hotspots lol

But to your point, isn't what you described most of the web?