Re: "though it has been given significant hardware upgrades over the years."
You should read all the researches that are based on Hubble data - data which are not "images" only. Those are what the general public may understand easily, but there are far more data than those. Spectroscopic data, for example. In a far large window.
Hubble never gained the "big discovery" - but it lead to a far better understanding and measurements of many, many space objects.
Sure, the bean counters count beans, they can't see beyond that. Webb costed too far more than planned too - and you see a shift, the first space scientific instrument to be named after a bureaucrat, not a scientist/explorer... guess why?
Also Webb is essentially an IR only telescope, with a few specific aims only - sometimes that attract also a lot of PR too like exoplanets - , and a far shorter expected life - hope it will work flawlessly for that, at least.
So a lot of actual Hubble capabilities will be lost when it will become inoperative. And some of those capabilities, for example UV capabilities, can't simply be replaced by ground based instruments - no matter how large.