[dom0]

> The same forces are at work on Python (or Ruby, which gets faster at every iteration.)

Python performance has been one step forward two steps back. For example, dict() has significantly evolved over time and some other things became faster as well, but most stuff just becomes slower as more stuff is added or previously native code is replaced by pure Python (see io in 3.0, which was reverted, or import).

Ditto for Python application performance. Python has exactly no zero-cost abstractions, so when something is refactored to use classes or big methods are split up, the result is almost always slower than before.