One of the reasons why Aikido is often considered ineffective is that aikido is not a sport and as such there is no competition in any form. Aikido techniques are always performed so that both tori and uke knows what will happen. And why is that? The base of Aikido are the levers on the joints and any resisting is a sure path to injury, and this is not the point of any training.
But then how can anyone be good in aikido when there is no sparring? And how one can test his technique? Constant repetition of the techniques over and over again leads to creating a sense of how, when and where something works, as well as to understand the principles on which the levers work. The purpose of the uke is to always acting as if he really attacks. In this way he helps the tori to learn the the technique better. As tori is more skilful, attack can be more powerful. Tori can always asks uke to grab him stronger or weaker.
Is Aikido better than other martial arts? Of course not. Every martial art is good. There is no bad martial art. But efficiency does not depend on the martial art, but the skill of the one who performs the technique. To be really good at any martial art it takes years of dedicated work. Talent plays a role too, but the commitment and work are much more important. Masters who practice for years have a very efficient and powerful technique. There is no way to have a powerful technique at any martial art without a long-term practice.
The difference between aikido and other martial arts is that, as there is no competitions, there are no rules in the sense that they exist in other martial arts. In the ring, there are rules, but there is no ring in aikido. Even a small distraction can allow a part of a second that you need for an efficient technique.