"Will that work on the street?"
"People don't attack like that!"
A recurring thematic question in any dojo is "will this work in real life?". Every martial art has some degree of formality and a set of rules of engagement. Boxing, for instance, is certainly applicable to a "real" life fight, but training in boxing is fundamentally a contest. Its training goal does not end up being self-defense, it is a contest of skill, strength, endurance, and heart. There's a ring that contains it. This just a reality of training is and is in no way a slight. These constraints are necessary to develop in that art. I only pick boxing as an example as it is likely to be most familiar to the most people. All forms of martial arts have constraints and rules of engagement. They are necessary and are not intrinsically bad.
Aikido is no different and therefore it is natural for students and observers to question our "formalized" attacks and set of techniques. Tsuki for example is not a common attack in the wild. The problem is that out in the wild, it's wild. There aren't standard attacks. There are skilled and unskilled people all over. Just look at security videos on YouTube and you will see that there are no end to the wild punches, half-assed kicks, and drunken tackles that no sensei would want representing their art. But, what those attackers lack in skill they often make up in fervor.
Techniques, whether in Aikido or any martial art for that matter, are specific "what-if" cases. It is impossible to imagine, let alone practice, every "what-if" scenario. So we need to select a common set of "what-if" cases that we can use to develop the principles of our art. They need to be common so that they can be knowable; so we can exchange ideas; and we can be able to evaluate progress of the integration of the principles.
This concern is not even unique to martial arts. How many people do you know that got hired to do algebra or calculus or read words. Those jobs are pretty slim. But there are lots of people who use those tools and concepts in their daily lives. Those techniques we learned in school are not their own end, they are a means to do greater things like build cars, launch rockets, stream movies, and write music.
So, no, people won't attack like "that" on the street, and no, that technique will not be 100% applicable to the street. But techniques are not the end goal. They are a tool for us to communicate and learn core principles. Get out of the way, relax progressively, upset their mind progressively, maintain our posture, feel and steal their posture, then lead them to fall, as hard or as softly as we need them to fall in the situation.
What can be a valid conversation is do we have the archetypes of attacks and responses covered by our selected "what-ifs". Did fashion shift and everyone is wearing batman gauntlets, well then we need new responses for hand strikes. Did we revert to 1700's architecture and all buildings have like 6' ft ceilings, well maybe we don't need the shomen (over-head strike) archetype anymore. These are silly examples but they illustrate the thought, do our archetypes cover the bases of both attacks and how we respond? So long as they do, then we can continue to practice our core techniques to develop the principles of our art. If they do not, then we evolve.
When Sensei Maruyama came to the United States, he had to evolve and change our cadre of techniques. The principles of Aikido were sound, but they playground had changed. People in the US were more varied in size and many are very big compared the Japanese population. Widely varying heights eliminated certain techniques as being viable general case solutions, so they went away. Western cultures never sit seiza in real life. So kneeling techniques went away. The "what-ifs" of Aikido Kokikai® therefore evolved because they needed to.
Any high ranking martial artist eventually comes to the realization that there is no technique.