mindless

Showing a lack of forethought or sense.

Having no sensible meaning or purpose.

An act of mindless violence.

“I Love Lisa” opens with one of my favorite underappreciated running jokes from The Simpsons: the passive-aggressive, quietly contentious relationship of radio jocks Bill and Marty, whose mindless happy talk regularly gives way to charged exchanges that betray the simmering resentment and disappointment perpetually lingering just under the surface of their relationship.

Heedless.

Near-synonyms: unmindful, absent-minded, thoughtless

Overly repetitive and unchallenging, not requiring any careful attention or providing any significant stimulation.

Near-synonyms: automatic, rote, dull

Lacking a mind.

Near-synonyms: brainless, unconscious, unsentient

Atheism alleges that mindless scientific forces control the universe.