What exactly is wrong with the client?

I'm seeing a lot of complaints about how Riot needs to switch back to the old client. But I personally don't have any problems with the client that we have right now. I mean, maybe the shop itself needs a little cleaning up, but the shop doesn't even get in the way and shout at me, "BUY THIS!". I heard it's slower than the past one. I never used the past one but this is good enough for me. It's neat looking and pretty organized and I'm satisfied with it. So what is the problem that you all have with it?