How so?
It simplifies everything.
It does, in theory.
They are in my experience (and that of plenty of others) very unreliable.
My dad had exactly the same situation as you; he bought a new TV but his older receiver didn't support 4K passthrough. That's fine, I thought. use HDMI ARC. It worked fine. Once. After that, when you turn the amp back on it would be a lottery as to whether it would actually output any sound. This is not helpful to him, or my elderly mother who just wants to turn on the TV and watch the news.
I ended up taking an optical output from the TV to the AVR. This works perfectly, and luckily he already has a (Logitech Harmony) universal remote with which he controls his devices. I just had to tweak its activity configs to fiddle with the input selections.
Other family and friends who have tried to use ARC with various all-in-one surround systems and soundbars have also struggled. My girlfriend's dad bought an LG surround sound/Bluray system to match his LG TV and even then it had similar issues to the above, and when it did work the volume adjustments through CEC were erratic. It seems he's now just given up with it and gone back to the TV's built-in speakers.
So you'll have to forgive me for being rather "old school" in my approach of wanting everything connected and controlled using more robust methods
