With an increase in technology, why doesn't NASA re-do a few projects?

We launched Voyager in the late 70s which had the same technology as a key fob, and the Hubble telescope was launched in the 90s, when cameras were advanced for that time but nowhere where they are now. My question is, why don't we re-do a few projects with better technology? My guess is that we are focused on... show more We launched Voyager in the late 70s which had the same technology as a key fob, and the Hubble telescope was launched in the 90s, when cameras were advanced for that time but nowhere where they are now. My question is, why don't we re-do a few projects with better technology? My guess is that we are focused on newer projects like going to Mars, but wouldn't a new telescope like Hubble with today's technology be able to capture much more or at least higher resolution photos? Or wouldn't a new Voyager-type craft be able to take better photos or travel faster or whatever we would want it to do?
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