I think there are a few misconceptions here. It is true, that we do not start in a bent structure. This has a lot to do with the concept of Zanshin. I would say, that for on armed, 1 on 1, combat, there are number of Arts that are better than aikido. However, we make 2 assumptions that most arts do not make. 1. every attacker has a weapon. EVERYONE has a weapon. Could be a bottle, could be a pool cue, could be a stick, could be a knife, could be a glass, there is always a weapon involved. 2. every attack or has friends. The fight will never be fair, and will never be 1 on 1. We assume always, that there will be another person joining the fight.
In those situations, when you are fighting against weapons or multiple attackers, Aikido is likely a better choice than many other arts.
Also, we could create the weight shift if we need. At lower levels, we train in a static, non dynamic manner. People have to feel and explore the movement of the technique. For example, I was working with a junior student the other night on shomenuchi ikkyo. He was struggling, as he kept trying to push my arm in a linear manner. I resisted, and demonstrated that he was not doing the technique properly. I showed him how to employ a circular motion that worked around the resistance. We always discuss where the resistance is, and how to work around it. At higher levels, the techniques by necessity have to become dynamic. Concept of sen sen no sen. You should already be moving before your opponent even touches you. This way, resistance can never be established. It takes a long time however to get to that level.
As far as creating weight shift, this is where atemi becomes so valuable. O'Sensei once said that 90% of his Aikido was atemi. What he meant by that, was reacting to an attack before it lands, and using strikes to off-balance your opponent before throwing. Unfortunately, most aikido dojos do not practice this. That does not however mean that it is not there.