If you go from non-functional to functional with extraneous crap that’s a success. Unless you’re working at the forefront of research or at the absolute limits

If you go from non-functional to functional with extraneous crap that’s a success. Unless you’re working at the forefront of research or at the absolute limits of your capabilities an explicit mental model of what you’re doing is of surprisingly little use. Even that exaggerates how useful it is. The huge majority of improvement is by trial and error, with shoddy and incomplete mental models. Your last paragraph is just what happens when there’s no force demanding quality. If there’s not strong pressure to maintain or improve quality decline is inevitable.