To play devil's advocate a little... if the trains had sufficient carriages and doors, then perhaps it would be quicker for passengers to alight/board thus avoiding those delays due to people trying to squeeze on or off. I do see your point though - there are now more stopping trains at Denmark Hill between 8 and 9am (which I assume are also stopping at other places too) and the trains, while busy, aren't as packed and are far more punctual than previously.

It's exactly the same story on buses. If the service is running frequently enough that it's not crammed, people get on/off quickly and the journey takes a far shorter time.

I do appreciate the complexity and can understand the odd delay here and there. What I (and my boss) find harder to understand is where the delays are everyday - in that case shouldn't the train be re-timetabled to meet its actual running time?