> Yes, some movies are boring, but those are bad movies.
Actually, in real life, otherwise good movies can have some less-good parts, and otherwise bad movies can have some individual scenes that are great. Life, and art, isn't black-and-white.
> If the middle isn't enjoyable, the end probably won't be either
You've clearly never taken taken a screenwriting course, or analyzed the many many movies with a saggy middle but a great ending -- which is actually an extremely common pattern. There's even a name for it, the "second-act slump".
> but it doesn't need to be painful to sit & do nothing for a bit. Once you get used to it, it stops feeling so uncomfortable.
Nobody ever said anything about it being painful or uncomfortable. It's just making better use of your time.