NASA has already made images of planets from the solar system before. So why is NASA/ESA making images of planets from the solar system by using the JWST instead of exploring unseen parts of universe?
Quite simple: JWST is capable of making images with much better resolution in a different spectrum.
Land based telescopes cannot make such clear images due to the atmosphere being in the way. Additionally, the atmosphere blocks some significant parts of the (near) infrared spectrum, which is the spectrum in which the JWST is producing images (which are artificially coloured afterwards). Additionally, other space telescopes produce images with much lower resolutions and in different spectra, e.g. the Hubble in the visible spectrum and the Herschel Space Observatory in the far infrared and submillimetre spectrum.