This is, of course, an exaggeration of the both of them. Each has its own use case in which it performs better than the alternative. In truth, I use ubo as much as I use reader view :)
You’re not the first one to ask this and I’m tired so I’ll just slightly edit my other comment. Only read bold parts if you’ve read that one.
where it makes sense
Firefox has a built-in function that checks if the extractable text from the website is “acceptable” and will decide whether to display the button. I don’t think the result of this function is available to extensions but you should ask Firefox devs, maybe add an enhancement request.
You can trigger it everywhere using
about:reader?url=https%3A%2F%2F[...]
You can use another trick: bookmark about:reader?url=%s and add read as its keyword (only in Properties window, separate from “tags”). Then put read␣ in front of any URL you want to view with Reader Mode!
There is also an extension called ☈ Redirector, which can do this for you automatically. However, it is rather clunky: you must create a Regex pattern to match URLs that you want to be affected, and you’ll need to temporarily disable the extension to exit Reader Mode.
