Is my room doomed? Pic

Lots of good thoughts above, and most likely several of the factors that have been mentioned are contributing.

But I would single out the short distance from the listening position to the windows as likely to be the most major contributor, despite the fact that closing the curtains/drapes does not help significantly. I would go so far as to say that I would be surprised if having a reflective surface like that so close behind the listening position did NOT cause the kinds of problems you are describing.

Basically what you are hearing is the direct sound from the speakers plus a lower amplitude version of the sound delayed by several milliseconds (as well as altered in frequency response, both by the reflective surface and by the fact that our ears respond differently to sounds arriving from the front and from the rear). To the degree that the reflected energy is strong enough to be significant, that results in comb filtering, with a lot of it being right in the mid-range based on the distances involved. My understanding is that that kind of effect would correlate subjectively with a general lack of clarity, or what you are describing as a veiled and muffled sound. There would also obviously be effects on imaging.

If moving your listening position forward, as was suggested, doesn't lead to a satisfactory resolution, I would look into the possibility of some sort of large sound absorbent panels that could be put in place in front of the windows during listening sessions, and put away at other times.

Regards,
-- Al

You would think closing the drapes would help if the windows behind the listening position were the major factor, but the OP indicates that closing the drapes did not make much difference, which is not encouraging.

"Is my room doomed?"

Never fear, the Audiogon acoustic hit squad is here!

Your name is not Smith and you are not a Doctor, are you?

An aside: waiting for 'breaking in': if the sound is not basically 90% or more there straight up, it's NOT going to magically arrive with breaking in.
It IS true some benefit from use arrives after a bit of time, and the many gushing: "at first it sucked, but after 100 hours it became perfect.." are typical audiophile nervosia exaggerations. If it sucked to start, it STILL is gonna suck afer breaking in, anything else is dealer bull#hit to stick you with something you do not really want.
The sound upon arrival should be really good, then with 'break in' it can become fantastic.
Somehow "breaking in" has become the magic bullet cure all phrase to stall the instantanious reaization that it is crap and you know it, and want to return it immediately.
I KNOW this is going to bring out a dozen stories how "I didn't believe, BUT..." but those mask the ten times greater stories "I got screwed because I waited... hoping.. and finally gave up.. sold it a year later and got what i wanted"
Waiting and hoping for a miracle is only benefiting the dealer. If it isn't right in your place, take it back.
(If you can't take it back, perhaps this diatribe will benefit others in similar situations)
IMO.

Break in is real in many cases. A

But also in many cases, you are screwed with no recourse if you wait for it to happen and it still doesn't meet your expectations.

Not sure what your exact contingency options are with the seller (hopefully there is some kind of satisfaction guaranteed policy) but do not loose the opportunity to return if you have it as a result of waiting for break in.

Enzo,

This is crazy, having people draw conclusions based upon a single photo of your room. It is a beautiful space, by the way. Do not despair.

I am having a very hard time appreciating the actual distances based upon that photo. Could you put some more pictures on your systems page? If the speakers are too far apart, the image may be thin. Too much toe-in with speakers too far apart can make it even more thin. You just need to start moving them around to know what is right.

Equipment break-in is very real, especially with full-range speakers. It can take several months of continuous play before the bass is appropriate. Without the break-in, the speaker can be very disappointing regardless of room and equipment.

Lastly, have you tried any other amps? I know many people like Gryphon, but the amplifier-speaker synergy is really key. I also know that many will advocate for the Rockport-Gryphon connection. However, I believe what the designer uses and shows with his speakers should be the start and not the end of your amplifier search.