While I agree that cathedrals have a lot of echo, I'm not sure I would like it if there were less. The reverberation makes it more difficult to understand sermons, but organ and choir music in a flat space could lose their power and ethereal qualities. I've seen it claimed that the acoustics of Notre Dame were part of what made its organ sound so wonderful. OTOH, there may be too much reverberation for symphonic music, which needs clear definition,