Slip n turn
It's going to be your aircraft when doors are closed. If you've been planted in your seat 45 minutes since you last had a look outside then manage the bloody thing by getting out and looking at it whilst you still have the chance so you know no other bugger fiddles with it again before you depart. If you don't know that the ground crew talking to you on pushback or their mate giving you the thumbs up and wave have done their own dligent external check on your aircraft too, and are competent to do it, then why are you leaving the apron?
With your logic the Captain would have to get out of the aircraft after the baggage doors were closed and the refuelling finished and do a walk around to check up on everyone just before departure on every single flight. If another department is working on the aircraft just prior to pushback the flight crew have to trust them to do their jobs to a degree. That's just modern aviation. You can't know for sure that they have " done their own diligent external check", you have to trust that as professionals, they have done their job. You're living in a fantasy land.