Agreed, and I also don't have a real answer. At least, not a technological one. The closest we can get it is a bunch of developers who care about a product, ask themselves lots of "why do we do it this way", and "could this be done better", and try to come up with some solid answers. Of course, with products that survived 10+ years of maintenance, it is highly unlikely that enough time will be afforded to any team.
Circling back to what I was trying to say with the first comment - I suspect the rapid development promise and culture back in the day led to a lot of these apps being developed. The tooling was just an enabler.