The word 'amateurish' often implies criticism or a lack of approval for someone's effort. His amateurish handling of the negotiations led to a bad deal.
Pro Tip 2/3
Non-professional
'Amateurish' is used to describe work or behavior that doesn't meet professional standards. Despite her passion for baking, her cakes had an amateurish look.
Pro Tip 3/3
Lacks Practice
Use 'amateurish' when someone's work suggests they need more practice or experience. His amateurish painting technique showed he was new to the art.