If my ukemi depends on someone else in any way beyond the initial taking my balance, I am doing it wrong. My ukemi is for keeping me safe, no matter who is throwing me and how......
Yeah, the times I find ukemi most valuable is when they _don't_ throw you 'right'. At first when you're learning how to fall you depend on nage to throw you in ways that make it easier to fall safely, but the more you train the wider the range of 'funny' situations that you can still come out fine from. Even if everyone you're training with is well-intentioned (and I wouldn't train with them if they weren't!), things happen, and IMO that's where ukemi comes in.
"NagaBaba, just look at ukes with Chiba sensei, it is very rare that they take high breakfalls and as you know he is one that can throw you very nastily. It is my understanding that Chiba sensei is not a fan of high breakfalls.So I think aikido can be done without that kind of ukemi."
Is it really about how 'nastily' you're thrown, though? To me it seems much more about what position you're in than how hard you're thrown. There are some situations where there are many options, others where there are constraints (e.g. your feet are blocked, your rolling arm is restrained, etc).
Anyway breakfalls are the physically softest way of taking ukemi I personally know (though there are different kinds, some more than others). A really violent roll feels a lot more vulnerable for me when I take it than a breakfall. For me it seems counterintuitive to deliberately avoid breakfalls unless I have some very specific injury that aggravates them.
In any case I'd rather know lots of different ways to take ukemi so I can adapt to the moment and take whatever feels safest or most comfortable at the time.