They travel in space ships from who knows how far and can't operate a door knob.
It wasn't that they couldn't...it was that they didn't know how. Doors (much less doorknobs) didn't exist on their planet.
Having a hive mentality and living on a planet without any weather influences, they never needed to develop dwellings. Or rooms. Or doors.
The interiors of their space ships had no doors at all. Since many of them had been born in space and never been on a planet, Earth was a baffling mystery for the most part.
How fortuitous that they happen to emit some paralyzing gas from their wrists to help them steal humans. What evolutionary cycle would give you gas emitting wrists? This movie was shit covered shit with shit filling.
But that wasn't a paralyzing gas. That was a pheremone spray that was intended to say "I surrender" if the creature on the receiving end had the right RNA receptors. Unfortunately, it had unintended side effects on humans. Oops.
And evolution has nothing to do with it. These are surgical implants.