The OP is emblematic of the "cocktail-party level of understanding" that leads people to discount how hard it is, and how much blood, sweat, and tears it takes, to build anything complicated, like a plane: https://danluu.com/cocktail-ideas/
It also downplays the absolute skill you need to be able to do even the “weekend session” and get something that’s workable - anyone can doodle a design in a weekend and even make changes to it, but getting one that’s actually a workable foundation requires people who know what they’re doing.
