If they could carry a larger payload, we could have a Hubble with a larger primary mirror. Some of the risks/costs of the JWST is all the folding mechanisms to fit the Ariane 5 payload enclosure.
It's kind of limping along. It could gather images for a lot longer but it's hardware like gyroscopes are starting to fail. IMO the money to refurbish it would be better spent making a new instrument and cheaper too since you'd just need to build and launch not launch, capture, land, refurb, and relaunch.