There seem to me to be two ways that Judo techniques can be made to work, the first primarily rely on leverage and force, employing sweeping legs, hip fulcrums, etc as the primary factors in making the techniques work. Tskuri, kuzushi and timing are important and contribute significantly to the sucess of techniques, but in terms of how the technique is being made to work they are of secondary importance.
The second way relies primarily on tskuri, kuzushi, and timing and the throw itself is almost of secondary importance. This is exemplified in the famous (infamous?) Mifune sensei video, where if you watch carefully the uke are pretty much done for before Mifune sensei ever steps in for the "actual" throw. He sets them up so well that the actual sweeping leg, or hip fulcrum or whatever just finishes the job.
Of these two the second is much harder to learn (may take a lifetime). In the bad old days of Jujutsu, if your method of fighting took 10 years of practice before you could make it work, you would be seriously short of students (high mortality rate during the learning curve). So the techniques had to be functional at two levels. The first could be relatively quickly learned and employed fairly effectively. After a single lesson learning a throw such as ogoshi, the student is way ahead of an untrained opponent. If the student continues his study perhaps he can reach the second level at least occasionally.
So, if there really are two levels of technique, then the second level is usually considered the higher, more desirable level (at least in the realm of self improvement or art which both Judo and Aikido strive for). In my somewhat limited knowledge of Aikido techniques it strikes me that they are mostly pretty mechanically simple. Very little in the way of reaping legs, hip fulcrum, etc are evident. They do not provide the raw mechanical advantage that can be exploited using strength and speed. This may be a basic characteristic of the root art, Daito Ryu (about which I know even less), but most other jujutsu schools I have seen tend to be more like Judo technique and employ many of the same mechanical principles.
So to continue my house of cards. The primary goal of Aikido is personal development, this being the case, perhaps Ueshiba sensei sought to skip over the first level of technique and try to push students towards the second. Perhaps there is a deliberate "handicap" there so you do not rely on sweeping legs or hip fulcrums, but in order to make the techniques work have only kuzushi, tskuri, and timing to do it with and so are forced to learn them (presumably without being distracted by strength-based technique). Since the primary goal of Aikido is not self-defense, and we live in much safer times immediate efficacy was not as important as it was in Jujutsu.
It is primarily low-level Aikido that sucks in terms of effectiveness, as would be expected if Ueshiba was taking the strategy that I suggest. High level Aikido is quite effective and powerful, but takes a long time to learn. Also, if people take off on their own (as evidenced by the plethora of different Aikido schools) before they fully grasp the higher level, they do not have the basic mechanical advantages to fall back on, and so you end up with empty dancing about because the techniques do not work unless you can use them at the higher level, and no one knows how so there is basically nothing there.
So in the end perhaps it is just a different route to the same end, perhaps that is what Kano sensei meant.
But of course I could be full of hooey.