It's a graduated step-by-step process, but it can be taught very quickly - that's what's on Ukemi from the Ground Up, and I've had a number of teachers contact me, thanking me for enabling to finally teach some of their problem students. I've presented this work at a number of dojo and many beginners are taking koshinage ukemi on their first day of class. Most within a week. So you can assert that it doesn't work, but I've got empirical evidence that it does. The flaw in aikido ukemi is revealed in this:
Correct rolling forward and backward develop flexibility. Then, they need to learn how to position their body in the moment of landing (which is completely different from rolling shape).
What you've just written is that rolling, in the typical aikido fashion, does not serve survival. And this is true - that's why "pulling up" is necessary, because the typical aikido roll (over shoulder and hip), which makes a beautiful "shape," does not position the body properly for a hard fall. (My method, really a combination of judo and sumo ukemi, stylistically, is not attractive. But it's a first step that enables one to choose
a more elegant style, confident that tori cannot gratuitously or inadvertently hurt you. As for pulling up, all I've said in that regard is that one should assume, until proven otherwise, that the other person doesn't know how to take a hard fall. The two people I inadvertently injured in koshinage were both more than competent - one an ikkyu and one a sandan - but "instinctively," when they found themselves thrown a little faster and from a higher position than they expected, they did not tuck their head and shoulder, because their hard-wired ukemi was to project themselves outwards (classic Aikikai style, all the way back to O-sensei). (This is not true in judo, fwiw - the legitimate assumption was that if you were on the mat, doing randori, you'd know how to take a koshinage-type ukemi).
In short, it is better to teach people how to survive the worst first. Then, the "open out" into a roll, by choice, when they know it's safe. For example, there are enough incompetent people and malicious people who will deliberately try to damage their partner in an "arm-bridge" shihonage, that if you assume that a person will execute the technique safely, so you can take a "back fall," you'll get your arm ripped out (I don't know about now, but this used to be an "Iwama-ryu" specialty with "guests."). But if, from day 1, you learn how to take ukemi in the POSITION for high-impact falls, you can "choose," when you know it's safe, to sit-out, so to speak, into a back fall, but if, even at the last minute, the individual tries to break your arm, you easily and automatically go over into a "high-fall."
Final evidence: When I've taught an ukemi workshop, the teacher of the dojo I'm guesting at often presents students to me who've been practicing for six months or one year and still can't take a roll. By the end of the class, they are safely rolling (over shoulder blade to small of back - the shoulder-to-hip roll the cause of their problem) AND they can, at least take the "jumping fall" from kotegaeshi.
Mainline aikido has had a problem in it's DNA, in that the roll we are taught (I was, from a number of teachers) is to create an ideal "shape" of a throw (witness related thread about "do we throw uke" or something like that), which makes the teacher look good, as opposed to taking ukemi to protect yourself, in response to something you cannot stop, avoid or counter. Rolling out, being projected, is a kind of luxury when one's safety is assured. One final point: learned this way, uke learns that they can restore their own integrity, rather than being a passive "victim" of tori - in other words, from day one in training, they learn how to begin to do Kaeshiwaza.