I have been banging on about this for ages.
Tracks that are basically the same as they were in 1928 (apart from Air Fences) and Bikes that are rocket ships in comparison to the original type of Bike that raced on them. You are 100% correct - the speed of the Bikes does need to be slowed. This would not, in my opinion, spoil the entertainment value - but it would be safer and less expensive.
I would imagine a few Engine Tuners would throw their hands in the air at what I am going to say next. Engines should be manufactured so that Riders themselves could work on them - this again would reduce costs.
None of this will happen though - too many vested interests involved.