The levelups are not a problem, I think the milestones are not achievable as only they have increased while our ability to score points (Food income etc.) has not. 6* do scor e a lot more points, but people dont save their 6* for lvlups specifically, they lvl them for raiding/war - and its only one char.
It takes 21million food to max a 5* and over 700 2* characters. That will only get you just into the second milestone currently - but we dont train 2* that quickly or gain food that quickly either.
Daily income of food from farms is just over 1mil, so it would take 3weeks to get enough food to hit the second milestone once - but in those 3 weeks there have been 4-5 lvlups with that required milestone.
Lvlups / Character progression is currently a broken economy, farms hourly income should be changed, when maxed, to 10,000 (from 5,700) and just make it 500 per farm lvl for quickmaffs - this would help but it would still be bad.