I cant say I like this changes as I already see a quite big drop in my own earnings. I have a few thoughts after seeings what is happening after the HF21:

Authors will get less from their posts come payout, but it also means you will be rewarded significantly more for curating content after the fork.

The theory behind this change is that with more emphasis on curation we will see more users looking to earn from manual curation instead of posting as much as they do.

How a plankton (less than 500 sp) is supposed to earn the SP now? His curation will not be very big and most earning were coming from the posts. The post payout was cut quite a lot counting the 20 steem penalty barrier.
The curation will not cover the lost anywhere near.

I hope that the average post will receive more manual upvotes going forward instead of bots.

I read that in many places: "small users will get more votes now". And where those votes are supposed to come from? Everyone is already voting and using up the VP. I know I don't have anymore spare to vote more...

Looks to me it will his the new and small users the most. To the point that they will leave. And it is gonna be very hard for them to grow account now.
While the whales accounts will earn more on their 20 steem posts + the nice curation for having big accounts.

I also think that people will be actually more eager to use bots now. It will help them reach the 20 steem value and they will not lose anything on their posts that way.
Wasn't the HF supposed to kick the bid bots in a butt instead of users?

This whole change will just make the gap between big fish and small fish bigger and bigger.