Here are the most common complaints I'm hearing:
1. "I'm a newly promoted Champ player and the reward I get is gold?"
You've actually been given 6 different coloured banners to choose from. This is one of the strongest points of the new tiered reward system. Previously, players would only use the highest reward they received since the rewards were linked to ranks. If I was a Plat player why would I use a Gold reward? In earlier seasons I would only look at the reward for my best accomplishment. Now that the rewards are free from ranks I can look at all the rewards I earned and choose the one I like best.
Furthermore, as Psyonix have stated, they made this change to free up the creative process when designing new rewards. Having to design each reward around Bronze, Gold, Diamond etc was extremely limiting and it showed every season when the rewards were boring, unoriginal and even tacky.
2. "I grinded to Champ and now I have nothing to show for it."
You literally have the rank that is shown to everyone, every game. You have the satisfaction of working toward something and achieving it. And to be perfectly honest I'm pretty sure one week after the rewards are distributed most people will be well aware of what reward corresponds to what rank. If you want to show off that you got Champ in S7 then go ahead and use your new banner; I'm pretty sure everyone already knows by now that the gold coloured banner is for Champ players.
3. Grouping the goal explosion rewards
I actually agree with most people that diamond should be in the middle tier with plat, and that Champ - GC should be the top group. But apart from that I don't really understand why people don't like the idea. Especially since it's an extra reward.
4. "The goal explosions are underwhelming and simply just different colours."
I've felt this exact way about most other season rewards. It is slightly concerning that Psyonix reasoned that the new reward system will allow for greater creativity when designing season rewards, but then they give us these 3 goal explosions that are similar to a previously existing explosion, and simply re-painted 3 times. They aren't bad though. I'm sure there are lots of players out there who don't have the money or haven't been lucky enough to find a flashy goal explosion. And these are definitely upgrades from the standard ones.