...In a recent training in the dojo, with knife attacks, the nage could simply not perform the technique, because I didn't want to give my balance away. And you know what the nage said? I was not "committed" enough.. Apparently, the cooperative confines of Aikido need an uke who has no sense of their body, balance and improvisation abilities. and this is called "committed". In my dictionary, committed means a person who does all they can in their abilities to perform something. And giving my balance away, or leaving my hand/arm hanging forever (instead of pulling back) for nage to grab is not commitment. It is illusion. I know this will come back to the necessity of Kata discussion, but the problem is that even in Randori, neither real commitment nor real atemi is used.
Pulling this post out of the middle of the thread because I feel like talking about it, your problem here is that you are a jerk. Not intentionally, perhaps, but you created a situation where neither you nor your training partner learned anything. Bully for you. Taking your description at face value, you went in with enough of a center that nage couldn't unbalance you, and that's how you left it. Nage entered without the chops to unbalance you and that's how he/she
left it. And a good time was not had by all.
So, yeah, kata means you have to work with the situation and the abilities of your training partner. If they can't unbalance you, give up enough so they can unbalance you by doing the right thing (whatever you were training). As they get better, give up less. Same with leaving your arm hanging out there--leave it out long enough for them to work through whatever they need to. As they get better, you should move more and more to real time. This is something you and your training partner can and should negotiate in the moment: "Slow that down, and don't go so easy on me. I'm not really getting the kuzushi." "Speed that up. Let's see if I can handle it if you rechamber the strike the way a boxer would."
It is true that some people and some dojos don't push themselves. They are happy with slow recovery and foolish strikes that throw the attacker off balance. It's also true that some Aikido sucks. (Sturgeon's Law applies.) If nage is depending on you to throw yourself off balance, and your dojo doesn't teach any way to create kuzushi... go somewhere else.