The proposed "better Hubble" that would launch in the 2040s is projected to cost $11 billion. That's a fair few servicing missions; it sounds like we can probably afford to do both, and if so, why not? Keeping Hubble around doing science longer is still useful even with a successor planned.

https://www.nytimes.com/2021/11/04/science/astronomy-decadal...

Since Hubble is at the upper range of LEO which made shuttle missions difficult, I've always wondered if they could make it slow down enough to lower its orbit more easily accessible for orbiters where part of the refurb is to refuel it so that it could get back to operating orbit.

Maybe not Hubble, but maybe the next gen?

when it comes to something like this you are forgetting the government redtape involved in building a new one is likely a bigger cost than the actual engineering building and launching.

Not to mention that NASA doesn't have the kind of blank check budget that the military has (by a longshot) — in a budget overview they may have to cut service for old projects to even get research on new projects funded.