I think a lot of the issue stems with putting the 40 in a compact package. It is not a caliber to put in a sub 4" barreled gun. It should honestly be in a full size 4"-5" gun.
One of the big pushes when 40 was first making a name for its self with law enforcement was grip size and gun size for female and male police officers that had smaller hands. The industry responded with smaller guns. Being a higher pressure cartridge than 9 and 45 it gave more felt recoil in the hand. Which lead to a fair number of bad shooters. Yeah you can add in the departments training and Qual standards. To the discussion, the cost of ammo etc. The fact comes down to it, High pressure rounds in small guns suck to shoot. They take time, training and dedication. Things that police departments often have to put in other areas.
Shoot a 40 out of a 1911 gov, or even out a sig 226, HK USP, or CZ 75 and i find it to be an enjoyable caliber to shoot. When you get down to the 1911 officers, emp, khar, mini
s, 239, etc then it is not so enjoyable and for new shooters it can be down right challenging. Bad shooters can develop habits that become unbelievably hard to get rid of.
Just like i do not recommend a 1911 for a first hand gun purchase, I don't often recommend a 40. Hell I almost always recommend a 22lr, either a MKIII, BM Camper or smith 617. Better training, cheaper ammo, less felt recoil, and certainly more fun to learn on.
I am not going to blame the cartridge, but the actions taken by individual shooters leading up to owning a gun of any caliber. The fact is the 40 is just as accurate, just as effective, and just as capable as either a .38, 9mm, 45acp, 357 round. It comes down to training, effort and time spent with ones firearm. When people swap guns every 3 weeks, because they did not shoot the last one well, then i loose all sympathy.
to use each gun specifically, or don't bother carrying it.