As has been stated before,the RESPONSIBILITY for the seats is the airline. I recently travelled on an airline whose name may not be spoken aloud here. The economy seats were narrow,hard and very uncomfortable. Pony up for business you say........well I did that on the return leg. Full bed...narrow hard and unpleasant. Never again.
Later that month Business class transatlantic on United 757 (the ONLY upgrade I have ever received) It was night and day. Stretched out COMFORTABLE and able to relax. Returned Y and that was tolerable.
As I am not wealthy and do not have a company to pick up the tab I will always try to at least find a Premium Economy product. Seat Guru is excellent as is Airline Quality dot com.
Some research will pay dividends......