I think, if anything, AL is getting better. The DM quests is working as intended, and I'm glad they get rewarded for all the extra prep and responsibility they take on. Only thing I wish would stop is the snowballing restriction list on magic item trading.
The other nice benefit of DM xp is that it helps populate the higher tier bases for people who want to play t3/t4 who otherwise couldn't.
Agreed, now I haven't done it yet, but if someone has 20 times they can play and chooses to DM 19 of them it's not unreasonable that the 20th time if it's a tier 3/4 option that they turn in all their hard work and games they provided for the community while growing it, to cash in and play that tier 3/4 module and be able to have an appropriate amount of items for the tier to enjoy something other than tier 1 play.