There are very few extensions that I trust, and to depend on an extension to do something as trivial as this is not worth the risk to me. This particular dark pattern isn't the darkest in the scheme of things.
The source code is literally 20 lines, very easy to audit. You can put the static download in your Mozilla folder to avoid auto-updates. It is a nice quality of life thing for me. But yeah definitely not necessary as you can always edit the URL yourself, as the extension author helpfully notes.
But that's 20 lines of code that I don't have to worry about just to get to a zoom link faster.
Let's face it, I'm about to join a Zoom call. How much faster do you really think I'm trying to get to it? This is actually one of those dark patterns I don't mind.