When you consider all the possible variables....
Sometimes you have to wonder why they work as well as they do. Autopistols are made to work best with one specific load, and work well enough with everything else. And it is that "everything else" that your "unreliability" usually comes from.
It is very rare to hear of a milspec 1911 from a quality maker choking on 230gr FMJ from a quality maker. Change the ammo, use aftermarket magazines, springs, change the specs on the gun (for accuracy, or any other reason), and things start to screw up at an increased rate.
The P08 Luger pistol is one example. The toggle action is very efficient, and works well, IF fed the right ammo. GI bringback Lugers had real spotty reputations for functioning, because for decades the 9mm ammo made in the US was underpowered by European standards.
Aitoloaders are made to work with a range of ammo, but that range is not infinite. For sime guns it is pretty narrow. Unlike revolvers, where anything that can be stuffed in the cylinder goes bang (nearly), autos are more picky.
The ammo is the most common cause of problems, either because it is out of spec, or it is not suited for the particular gun. Some guns are not made to feed everything. Some will feed empty cases. Most are somewhere in between.
The majority of the time when an autopistol doesn't feed right, (when it isn't the ammo) the problem is the magazine. And even good magazines can wear, or get bent and become less than good over time and use.
I have never had an autopistol that didn't jam. Shoot them enough, use enough different ammo, and sooner or later you will get a jam. I have had guns that will jam often, if not treated a certain way and fed certain ammo, and I have had guns that have gone several hundred rounds, or even a couple of thousand without any problems, until they hit a bad round. And you really can't blame the gun if you feed it bad ammo.
You can jam revolvers too, you just have to work harder at it! And again, most of the time it will be the fault of the ammo.
I have one of the little Jennings pocket .22s, (which I was given by a disgusted owner), and I keep it around as an example of its type. Sometimes this little gun will run a whole magazine without any trouble, and sometimes it jams nearly every other shot. I keep it to show what a pistol shouldn't be.
What makes a reliable autopistol? Only your standard of judgement. Given enough round, or crappy rounds you will get a jam eventually. Not cleaning and lubing the gun is another good way to have it malfunction. I am quite satisfied with guns that I have shot for hundreds of rounds (with good ammo) and have given me no problems. On the other hand, if the gun can't get though a couple of boxes of ammo without choking, it isn't reliable enough for serious use.
We used to say that after the gun was broken in, 300 rnds with no trouble was reliable enough to be counted on. It is an arbitrary number, and if you aren't comfortable with it, pick one of your own. There is no magic number that says if you can go XXX number of rounds you will never have a problem. All there is, is your confidence, and what ever number of rounds you feel is enough for your confidence in your gun, and your ammo.
I would be confidant of a pistol that ran 800 rounds of ball ammo without a hitch, but jammed 3 times in 150 rnds of hollowpoints, as long as I was using that same ball ammo. I would not be confidant using those hollowpoints.