well, you can put any other launcher on it. try the google launcher or nova.
or, a windows phone or ios launcher if you fancy that.
I don't currently have an S6 to test on.
HIstorically, Many people have had a lot of negative opinions of Android based on their experiences with Samsung phones.
This is rather unfortunate, because Samsung's iteration of Android is not indicative of actual Android. Samsung goes out of their way to obfuscate most of googles android behind their fork of the operating system.
Touchwiz isn't just a launcher. There are fundamental changes to the underlying operating system. Samsung does it as much as they can get away with, while still being allowed to be "android" and run google services.
many people have made comments (around the world, not just online) that Android is buggy, slow, cumbersome, laggy, with too many things in too many places that arent intuitive or logical. But they're basing this off Touchwiz. Not Actually Android. The experiences are two completely, utterly different things.
And i'm not speaking out of assumption here. I have owned a few devices, some samsung, nexus, an apple device in the past,. I like shiny and I don't hold myself to any particular vendor just because of a brand. Touchwiz has by far, been the worst OS / Android experience I have ever encountered. So much so, that on the two Samsung devices I have owned in the past, I eventually always wiped it and went with a stock android ROM