Well, Crumpp is basically referring to really high speeds, where the 109 was definatley "heavier" than the U.S. Fighters in particular, so I get his point there.
The 109 in combat had two things in its favour, which helped its pilots to rack up so impressive kill numbers
Firstly: Situation. Plenty of targets, and due to that, the engagements were often only executed under favourable conditions. Hit and getaway, - typically diving away after a pass, or if things went bad.
However, on the western front in 1943/44, it could not count on that any more.
Secondly: Speed. The 109 was always about as fast as the fastest planes the enemy could mount. It enjoyed speed superiority over enemy fighters for long times in many theaters. That is a pure and undisputable fact.
So, up-to-date with everything, perhaps not. But definately not that obsolete.....