I love big reverb, but it does come with a price indeed. Back in the 70s, I went to a recital at L'Oratoire de St.-Joseph in Montreal, home of a 5-manual, 78-stop Von Beckerath. This is an Art-Deco version of St. Peter's Basilica, smaller, of course, but with about 9 seconds reverb. One Bach piece, in G-major, had a fast tempo. The G.O. 16' Trombone and 8' Trompette in the left hand, an 8' flute and sesquialtera in the right, you could make out the melody in the right, but the reeds were all smeared.
I think one reason for this, is that in the dome, soundwaves keep going all over the place and intersect themselves.