A cartridge has 4 components: case, bullet, propellent, and primer. The case and bullet need to be of an exact size or else it will cause a jam. The propellent must be appropriate for the bullet weight. The primer must go off when struck and ignite the propellent.
That's a lot to go wrong, but rarely does it seem to happen that a malfunction occur and the ammo is to blame. At least for me and those I shoot with, I've only seen rimfire and really old surplus centerfire ammo cause a malfunction. The surplus ammo was Serbian or Russian 7.62x54r and showed some corrosion.
As for the ammo firing at a consistent muzzle velocity, that's another story. I'm sure that varies quite a bit. Perhaps it's the primers that have seen the greatest advancement in quality control across the industry.
Even rimfire. I remember back when I started shooting in the early 90s, which wasn't that long ago, I would have a pile of unfired rimfire cartridges at my feet. I used a Marlin .22 LR rifle, so there are more variables than the ammo, but I rarely have rimfire ammo fail with a Ruger 10/22 or CZ 452. I've fired over 10,000 rounds of .22 LR between those two rifles. Out of that 10,000 rounds, I've had maybe 3 fail to fire.