I mean, the JWST is just bigger. There's two sources of unique solutions in the JWST, its size and the range of wavelengths it observes. The Hubble Space Teles

I mean, the JWST is just bigger. There's two sources of unique solutions in the JWST, its size and the range of wavelengths it observes. The Hubble Space Telescope had a ground-glass mirror which was absolutely massive, both in size and literally in mass. To scale that up, a beryllium-gold mirror was necessary to be able to launch it at all, considering the immense weight of a ground glass mirror. Similarly, to fit it in the fairing, it had to be segmented. Due to the size, it couldn't have an enclosed tube as that wouldn't fit any fairing, and the mirror would be segmented as well anyway, so it's just easier to go without a tube and hope really hard that you get no interference. Speaking of, the JWST operates at such large wavelengths that incredibly cold objects are practically giant lightbulbs to it. Point it at the cold, dark moon and you might overwhelm the sensor. Therefore the entire thing has to be as cold as is theoretically possible, which is here done through just putting a giant sunshield and big radiators on it. Size, again, so it needed to be a very innovative folding sunshield. Everything that it has isn't really "outside the box", it's just the only working solutions to practical challenges with scaling up something like the Hubble, and moving to the observation of ever colder, further away objects.