Threats keep evolving — a defense that can't adapt is meaningless.
Literal
Threat [topic-は] change continue, evolve-unable defense [topic-は] meaning [subject-が] not-exist.
脅威 'threat' and 防御 'defense' — could be military, cybersecurity, or metaphorical. 変化し続ける 'keeps changing.' 進化できない 'unable to evolve' uses the potential negative. 意味がない 'is meaningless.' Punchy, aphoristic — sounds like a military doctrine or security principle.