Not sure if tools and technologies can solve accidental complexity.

In my opinion, a system that has been stable for years isn't 'mature' in a good sense. An exceptional system is one that can still change after many years in production.

I believe this is almost impossible to achieve for enterprise software, because nobody has incentive to make the (huge) investment into longterm maintainability and changeability.

For me, consistent systematic naming and prefixes/suffixes to make names unique are a hint that a person is thinking about this or has experience with maintaining old systems. This has a huge effect on how well you can search, analyze, find usages, understand, replace, change.