I agree that the "new" Mazda seats are terrible. I had a 2006 5 which I loved, so bought another one (2012) this past February. The seats are horrible and I'm desperate for a solution. No kidding, this seat has just about destroyed my already sketchy back. I had to get a lumbar injection in May and now that it has worn off I'm very close to selling the car. I went into the seat back and added a homemade insert to increase the lumbar support, but in my opinion the real problem is the hard and non-compliant seat bottom combined with the firm suspension. I can feel each bump pounding my spine. For contrast, and as others have said here, when I get into my wife's Edge or rental cars with nice seats I can feel an immediate difference. In fact, my wife and I traded cars for a few days and she can't stand the Mazda seat, so it's not just me. You can find many comments about these terrible seats on this forum and elsewhere.
BTW, I checked out the other Mazdas to see if I could get one of those seats and put it in mine, but found that they all have the new crap seats. The ergonomics AND the foam cushions are very poor. You can find older model used seats from auto parts dealers on eBay, but I don't know if I should bother trying that or just bite the bullet and switch cars. I'm afraid that if I went to the trouble of buying an older seat that it would either be disgusting, defective, or just plain wouldn't fit.