The problem is that so many practices we have gravitated to are actively harmful to performance. Worse, they are borderline harmful for maintenance. Specifically, some practices are better for larger teams than they are smaller teams.

Difficulty in that last is that the best practice for how to maintain code changes as you get older on the project. This is easy to see in code that is a bit of a mungled mess. But it is also visible on code that it is a beautiful stalled out mess of needing too much to get small contributions in.