I think this is the core of it. Just like dose makes the poison, dose also makes the addiction.At the doses utilized clinically I see virtually no abuse or addictive potential.
We all experience this with amphetamines - patients can be stable for decades on tens of mgs of stimulants daily without real concern for addiction, but if a person starts using hundreds or thousands of mgs... This also applies with opioids. For example, tianeptine was used for decades as an antidepressant, and reportedly quite a good one, and no one seems to have even suspected it was an opioid agonist in all that time even though it turns out that's probably all it is. Importantly, the therapeutic dose was tiny, on the order of 1 MME (mg morphine equivalent) daily per my calculations.
As an aside, in my view, the primary value of ketamine is that it allows the use of opioid agonism for mood/anxiety disorders without admitting that we are using an opioid.