Yes - get a FRETLESS and play it.
the best advice I can give anyone regarding playing FRETLESS bass is from Jaco Pastorius (whom while never seems to win ‘greatest bassist of all time’ polls in 2020) is by far one of the greatest innovators and fretless bassists of all time. His advice: “practice fretted bass!”
practice FRETTED bass, huh??
there are probably 2 big reasons Mr. Pastorius shared this with us:
(1) optimal left hand technique on fretted bass in placing one’s fingers right behind a fret. This builds produces the most accurate and clean sounding note. This muscle memory finger placement accuracy transfers over to the fretless to enhance intonation.
(2) practicing fretted bass allows the player to focus on playing BASS, and avoiding all the pitfalls of “mwah” and slides that can overtake a fretless performance away from playing real supportive bass. Even if fretless - the player still has the obligation in a band setting to provide the musical foundation for the entire ensemble.
finally — what has helped me is practicing diatonic scales and arepegggios (ear training), playing along with vocalists, and practicing Bach’s Cello Suites.
so — yeah, get a fretless bass and play the heck out of it!