Your pics help . . . That is a beautiful room, but not, just,as,you have been telling us, not overly HT friendly.
Your center seems to be in an acceptable location and angled up for seating positions, aimed at peoples ears.
All of the openness behind the top half of the fronts is not near enough to a solid back wall to carry or reflect sound forward as one would want.
Your sides have it tougher, again, not near a solid reflecting wall to capture sound and push It forward. Not clear to me,,but are they at ear height so listeners,seated,position or a little too high on the stands for that? You could try adjustable wall anchored speaker stands which you could install pointing them at center seated positions; or move them to ear height a little behind the couch.
Wherever you put them, I sincerelyrecommend you purchase from Amazon a lesser,expensive spl meter. Run Audyssey again but with a used,or borrowed tripod. Then sit in the primary seating position with the remote in one handmandmthe spl meter in the other, and level each speaker by ear to get the best eq'd level for,each speaker. Many people have to tweak post-Audyssey settings with an spl meter, to get something that feels to the ear a more balanced sound.
live with the sound result for a few days, then tweak,again, until you,overcome to your ear a more meaningful result than you are getting after an Audyssey only run.
i know it seems like an inconvenience, but could, as it has for others, yield, in the end, a result more to you liking.
anyway, IMO I encourage you to try it-- Audyssey alone is not cutting it for you. Again, doing tweaking Audyseey setting with an spl meter will get you closer to,a,more pleasurable result.
It should make a difference for you.
others,may have differ, but it seems you are getting a result you do not like--time to get an spl meter?