Your stadium sounds dead because the safety rules say so

A bowl that carries a chant beautifully is a bowl where an evacuation announcement cannot be understood.

Every bowl I have stood in has the same argument built into its ceiling, and almost nobody in the crowd knows it is there.

An announcement in a stadium has to be intelligible. Not audible, intelligible, which is a stricter and measurable thing: a specified share of ordinary words must be correctly understood by a listener anywhere in the seating, under the assumption that the building is being emptied in a hurry. That requirement is written into safety certification. It is not optional, it is not negotiable with a design team, and it drives more of a stadium's acoustic character than any architect's rendering will admit.

Now consider what makes a ground sound loud. Reverberation. Hard surfaces, a low roof that returns sound to the seats rather than letting it escape, an enclosed bowl where noise from one end reaches the other slightly late and thickens into a wall. Long reverberation time is exactly the quality that produces an atmosphere people travel to experience.

It is also exactly the quality that destroys speech intelligibility, because each syllable is still bouncing around when the next one arrives, and the announcement turns to mush. So the acoustic consultant arrives with absorptive material, and it goes on the underside of the roof and the back walls of the concourse openings, and the reverberation comes down to a number that passes certification, and the ground is measurably safer and noticeably deader.

There is a way out and the better designs use it. Instead of deadening the room, you distribute many small loudspeakers close to the audience so that the direct sound reaching each listener is much louder than the reverberant field. Get that ratio right and you can keep a hard, loud, reflective bowl and still pass the test. It costs more, it needs more cabling, and it requires somebody to argue for it early, before the roof section is fixed.

Which is why old grounds sound better than new ones. It is not romance and it is not the fans being more passionate in 1974. It is that those roofs were built before anybody was measuring, and the fabric of the place happens to hold noise.

If your new ground sounds flat, blame the specification, not the supporters.