It actually does fairly well. It's not quite the match it was when I had a Thiel center, but it's also not exactly like I sit there noticing a mismatch. I definitely use the EQ of the surround preamp to help. I have a general attitude about this stuff that doesn't necessarily work for...
My L&R speakers are Thiel CS 3.6. I had to replace my center a few years ago, and since Thiel is gone, I looked for an inexpensive alternative. That brought me to ELAC, and an original UniFi. I'm starting a complete update of most, if not all of the speakers, including sub(s). The Thiels...
I will be upgrading my system with UniFi 2.0s for surrounds, shelf mounted, and Debut 2.0 in-ceiling for Atmos. I'll be doing a write-up on it all once it's done, but that will probably be a couple months.
You simply can't make a blanket statement like that. Ideally, speakers shouldn't be close to a wall, but there are definitely plenty of speakers that are specifically designed to perform quite well when on a shelf. Typically by being sealed enclosures or front ported.
...and I suggest you just continue to post here, where people can see the entire discussion, rather than splitting it between here and the general thread.
That's a much better use of the room. As it is, you're so far from the screen and sitting against the back wall will never take full advantage of surround soundtracks. As long as you have room to walk behind the rear row (say 3' or more) then you can take decent advantage of 5.x.4 or even 7.x.4.
What are you doing for audio in the theater room? Regarding an earlier question, 5.x.2 probably is as far as you need to go, since the seating is against the back wall. To make decent use of an additional pair of surrounds and Atmos, there really needs to some space behind the viewing position.