Aha! The solution to the problem. Instead of louder instruments, better listeners!

What's happened there is that everybody takes music for granted now. You can listen to it anywhere and everywhere if you have a portable stereo; you are subjected to it whether you like it in some places and if you want to hear a live performance you don't have to wait till it comes to you, just jump in the car and drive there. Whereas music in the home was once the privilege of those who could afford to pay a staff of musicians (Like Haydn's orchestra at the Esterhazy court), now you just press a button and you're spoilt for choice.

It still doesn't explain why 500 year old churches suddenly need a PA now.

Anahata