It’s one thing to not understand your car alternator when you can call a tow truck, and quite another when you’re traveling light years in interplanetary space. Plus we do see things getting fixed, but it’s never in detail. In Star Trek you get plausible technobabble: “We can’t go to warp because all the relays are blown on the nacelles, and it’ll take at least 4 hours to replace them.” In SW you get “We can’t go to light speed for some undefined reason. Let’s watch Chewie moan angrily while smacking something with a wrench, then R2 shoves something in a hole and gets blown across the room via electric shock. And now the hyperdrive works.”