I guess the related questions is, compared to what?
The 'HST' has made many impressive discoveries in its brief operating life to date.
It produced confirming observations that now clinch the argument that supermassive black holes exist in the cores of at least a few nearby galaxies.
It discovered and imaged hundreds of proto-planetary disks orbiting stars within the Orion Nebula. It also produced spectacular images of the destruction of many of these disks in Messier-16 'The Eagle Nebula'.
It produced the first images of the very distant, young universe only a few billion years after the Big Bang which show numerous small clumps of intense star-forming activity colliding and assembling into larger more familiar types of galaxies, thereby confirming that galaxies form from the 'bottom up'.
It has produced startling images of stars in their death-throws ejecting planetary nebulae and gas at high velocity, and in beautiful asymmetrical patterns, which show that this process is dynamically very complex.
It has imaged the surface of Pluto and for the first time revealed details showing a complex surface covered with various high-albedo ices in an irregular pattern.
It has produced daily and weekly images of Mars, Jupiter and Saturn and several moons such as Titan and Io showing rapid changes at a resolution previously attainable only with 'fly-by' interplanetary spacecraft.
It has produced spectra of the famous Beta Pictorus circumstellar disk showing that its interior zone, about the diameter of the solar system, has been evacuated of gas and dust, and seems to be populated by numerous cometary objects indicating a primitive solar system has formed, although no planets have been detected as yet.
It has revealed that the immediate environment surrounding quasars contains galaxy-like systems in which gas can be seen streaming into the central core to fuel the quasar.
It's 'Key Project' of determining the Hubble Constant has resulted in a rapid convergence to a number near 65 km/sec/mpc which conflicts with the age of the universe based on old globular cluster stars and an assumed 'critical density'.
These are only a small number of the dozens of major discoveries to date.