The stormtroopers aren’t intimidating in R1 and Solo, the Empire is intimidating.
The Empire is at a part of it’s existence where their policy is scorched earth, our way or the highway. They’re kinda like the Russians in WW2, they got some cool toys but mostly they’re poorly trained and armed conscripts and if you have to deal with 300,000 soldiers on a planet you send 3,000,000 soldiers at them and 75% of those guys are going to die but you’re going to achieve your goal. By the time of ANH they’re pretty comfortable in what they’ve done and the compliance it has fostered and the slack is setting in.