Aircraft maintenance engineers are NOT supposed to build airplanes.......Physical exhaustion yes, mental exhaustion a very resounding Yes, an ill-informed loser like you won't understand cos you need to first lift the veil....and stop living in a vacuum...
And they get paid 70/80K to identify bugs, screen test, check controls and a whole lot of other stuff which a dingbat like you won't get.....and yes, they probably deserve more than the 70/80K they get right now....