Cancelling the rewards means cancelling Steem itself. Rewards is what makes most people come here not to reddit or medium.
As for your suggestion of letting the users tip the content creators, a very good project has been working on just that: the Brave browser and the basic attention token (BAT). Give it a look.
I argue that the tipping system is a much superior system than the reward system to attract new users to the system. I explain the reason in my reply to @biophil's comment above and I'm going to publish a post about that, so please keep in touch.
I'll take a look into Brave. I can't say anything about it at the moment, because I don't know anything about it.
Followed!
Then, you will be surprised.
I took a look at the Brave browser and BAT. It looks like an interesting project. The only caveat is how to measure human engagement with the content. How to distinguish between bot consumption of content and human consumption of the same content. If they can solve that problem, it will be a big success.
They have a very good team behind it. If someone can do it, they are the ones.