From what I understand, the /evolve debug command is made to force evolution upon a pokemon. The message "this pokemon cannot evolve" shows up in the feed when attempted.
This debug command can't do that unless what I stated above is done, I don't know if it's intentional or not.

Greetings,

There `/evolve` is more used to bypass the level requirements.
There is a parameter -f that you can use to force it to evolve it without other conditions.
The syntax would be /evolve player slot# -f