Doubtful
Part of speech: adjective
Definition: Subject to, or causing doubt Experiencing or showing doubt Undecided or of uncertain outcome Improbable or unlikely Suspicious, or of dubious character
Example sentence: The Vietnam War and the Iraq war, in different ways, both made me feel like I could not not address them. I'm very doubtful about the usefulness of poetry to do that.
Dubitable
Part of speech: adjective
Definition: Capable of being doubted; susceptible of being questioned.