re: Why are the tiger stadium speakers so bad?

It’s not really practical.

Those foam tiles you see with the pyramid shapes cut into them don’t really work. They are only really useful for flutter echo (like when you clap your hands in an empty room and hear a ring) at high frequencies. They aren’t nearly deep enough to absorb the frequencies that actually matter for vocal intelligibility.

For that, you would typically use larger acoustic panels filled with mineral wool, usually in the neighborhood of 2-4” deep (deeper = absorbs lower frequencies). Mineral wool can’t get wet, so that’s a major problem. The panels are usually covered with fabric, as the cover material needs to be somewhat acoustically transparent. If you put something like wood or metal over them there’s no point because then the cover just reflects sound.

So you’d have to have some sort of waterproof acoustically transparent material to use for protection. Then you’d have to cover the entire south upper deck with panels. And even then, they still might not absorb at a low enough frequency to fix the problem. They would probably be an eyesore and they’d definitely be impractical.

In a live sound setting, a crowd is often the most affective room treatment. People do a good job of absorbing high frequencies. I don’t think the high frequencies are the problem.