28 years in space is a long time, and the new JWST has a 5x larger collection area and is fundamentally capable of detecting a much larger spectrum (the mirrors are kept colder). The HST has cost more to keep operational than it did to build at this point, and its construction was not smooth. Money might be better spent elsewhere.
However, there is a HUGE amount of data still to collect from space-based telescopes. Even a crippled HST is a desperately wanted resource. It benefits us to have as many space telescopes as we can right now.
