I'm actually surprised as well. Ultimate was by far my favorite league to play in. There were never large draws like 45 people, but when I started about 3 years ago there was about 30 in the 5.0 division. I believed their forced promotion for the finalist and runner up is what has caused the issue over time.
The first season I played the players were mostly strong 4.0s to mid level 4.5s in this division with most players at the low 4.5 level. It has now degraded to the mean at about the mid 4.0 level due to people being bumped up. I have also improved which has made this a bigger issue to the point that I wouldn't have played if I hadn't gotten bumped up.