It only leads to negative outcomes if that's the only step you take though. Most societal problems need to be tackled from multiple angles to actually see any positive effect.

Rent control is a good tool for keeping existing tenants in their homes. That has a lot of value in itself but it must to be coupled with the construction of good quality, affordable public housing at or below the average rent controlled property in order to maintain the desired goals of keeping rents/property prices down for new entrants and increasing mobility.

The only issue with rent control is that it's applied as a band aid without also addressing the root causes.