[Robotbeat]

SpaceX is working on Starship, which should be capable of Shuttle-like service missions. (JWST is much more fragile than Hubble, however, so you'd need to build a custom servicing solution... but JWST is not representative of space telescopes generally.) In fact, SpaceX is counting on Starship to deploy their full constellation. No Starship, no 12,000 satellites.

[rtkwe]

I think JWST is going to look a lot like the future of space telescopes. There's hard requirements that make larger satellites better for observation, principally because larger aperture == better resolution and also because the larger mirror gathers more light so we can look at dimmer objects.

[Robotbeat]

It's not the size of JWST, it's the fact that it's deeply cryogenic and uses enormous, fragile multilayer insulation to remain so.

Indeed, larger apertures will be used increasingly. And this megaconstellation actually enables that indirectly. SpaceX is counting on their Starship launch vehicle to deploy the vast majority of their 12,000 satellite constellation, and indeed large launch vehicles (particularly reusable ones) require a lot of payloads to justify their development cost. But large launch vehicles also enable ever-larger telescopes, whose cost is only affordable if those launch vehicles are reusable.

NASA is already buying into it. Here's NASA Goddard tweeting out the larger-than-JWST concept called LUVOIR inside SpaceX's Starship (which again relies on the megaconstellation for demand): https://twitter.com/nasagoddard/status/1116310431969239040?l... ...and yet larger apertures will require in-space assembly over several launches, again only really affordable if there's enough commercial launch demand (i.e. from megaconstellations in particular) to justify these large reusable launch vehicles.

My point of view is that if we're going to be a really spacefaring civilization, it's reasonable that you'll be able to see human artifacts in the sky. Starlink is actually fairly easily stealthed, but other things (space based solar power stations, large space stations, in-space manufacturing depots, etc) may not be so easily hidden. Is the fact that human artifacts may be detectable in the night sky reason enough to disallow spacefaring?

EDIT: Note that the IAU letter is way more reasonable than almost all the media takes on this issue.