ineffectual

not sufficient to produce a desired result

• “an ineffectual effort to block the legislation”

not producing an intended effect

• “an ineffective teacher”
• “ineffective legislation”

producing no result or effect

• “a futile effort”
• “the therapy was ineffectual”
• “an otiose undertaking”
• “an unavailing attempt”

lacking in power or forcefulness

• “an ineffectual ruler”
• “like an unable phoenix in hot ashes”