Complexity has to go somewhere.
Because systems are just piles of abstractions and conventions "easy to change" is very relative. A compromise will always be required. A simplification here means pushing complexity somewhere else.
What I think is a practical way to see it is to have a good match between your audience mental models and the system conventions.
> A simplification here means pushing complexity somewhere else.
And it is a good idea to concentrate complexity on a few small pieces of software that only experts are contributing to. Think your typical web applications and databases: your app doesn't need to think about how data is laid out on disk and how on-disk indices are implemented; all of those complexities are pushed into the database. It's a good compromise.
What I think is a practical way to see it is to have a good match between your audience mental models and the system conventions.