I don't think it's possible to abolish prisons for all crimes. But why does a thief or a drug dealer (or worse, just a drug user) need to be in prison? What about the nature of their crimes necessitates imprisonment as a reasonable method of corrections?

If the point is stopping people from reoffending, prisons don't do that. Like objectively. Recidivism in the US is super high, and going to prison predicts increases in the severity of crimes people commit.

So, what reduces recidivism? Eliminating the factors that drove them to crime in the first place. So, you monitor them closely - house arrest, assigned social/case workers, etc. Like a more robust parole system for nonviolent offenders. With enough surveillance, you can reduce the likelihood of reoffence by making the chances of getting caught much higher. This enhanced monitoring would be temporary.

For violent offenders and more serious criminals, maybe prisons are still necessary. But they don't have to be dehumanizing and can provide necessary health/psychiatric, educational, social, and job skills training.

You could make the corrections system more effective by making society easier for criminals to reintegrate into. If you're a felon and you can't find work because you're a felon - how are you going to afford to live within the confines of the law? Step 1) jobs programs for felons with a path to eliminating non-violent offenses from your record as it relates to work with exceptions as necessary. Step 2) improve the education system to prevent people from turning to crime and to help give former criminals relevant job skills to earn an honest living. Step 3) provide healthcare to people - having access to healthcare for mental and addiction-related conditions is super important to reduce crime.

Basically - prison abolition isn't about just letting rapists and murderers go free with no consequences. Instead, people in favor of prison abolition are typically in favor of reducing the societal pressures to commit crimes and preventing reoffense.