Check out the all time lists in both events.
In High Jump there was a monstrous progress in 80's and early 90's. But now, nobody surpassed +2.40 (outdoors) since mid 90's. In fact, the best outdoor jump of the last 15 years was 2.38.
In the mile (except for Allan Webb, and here I open a big parenthesis) nobody has broken 3:47.9 in the last 10 years. 4.84 seconds slower than El G' World Record!!
What are the reasons?
Stagnation in training methods?
Massive doping in certain periods?
Lack of talent/genetic disadvantages?
Sedentary lifestyle combined with poor eating habits?