I've worked on quite a few projects that would have had significantly worse user experiences if they were done in a purely SSR driven way:
* Chat applications, or anything where you need to have the UI react to incoming events from a socket.
* Applications where sensitive data lives in the client and you don't want to be liable for that passing through your servers.
* Anything dealing with video or audio (e.g. video chat, screen recordings.)
* Applications that are driven by peer to peer data.
* Applications with high interactivity (e.g. spreadsheets, heavy form validation, drag and drop UIs, graphic manipulation.)
It really depends on what your application is doing. If you're just a blog or an eCommerce site, it's definitely worth asking if you need a frontend framework. But for some applications it's absolutely worth it.