Isn’t it that Old Ben was thinking of highly trained clones and had pretty much no stormtrooper experience in decades?

Like, he’d been living in a hunting the middle of a desert for 20 years intentionally staying away from anything dangerous.

As usual the fans come up with a great answer to explain away poor writing.

Or people are too dumb to understand decent writing. The storm troopers destroyed the rebels in the opening scene. They killed almost every fighter in the battle of Yavin. The only time they didn’t perform well is when intentionally letting Leia escape. Sure there’s plot armor, but there’s also an explanation for a lot of it.

For Leia, Vader had set the Stormtroopers on ‘Stun’.