Re: Aiki vs useless waza ?
From a skill acquisition point of view drills or blocked learning (such as structured solo waza in a class context) is very good at translating/ developing skills quickly to a certain point. However the learned skills tend not to be so robust under pressure and can lead to a false sense of confidence/ complacency and can actually go backwards. Ways around this are to introduce a random element (randoori, sparring etc), stress testing (such as the uke nage dynamic and other less traditional methods) and feedback (auditory, visual and kinesthetic) be it self feedback or external/internal feedback.
In the traditional context the arts seem to already cover many of the bases in developing and honing skills. Wether through solo drills using a partner for feedback (ki testing, resistive load on ikkyo/funakogi and some of the IS exercises that develop self feedback maybe? (that s a question 'cause i don't know enough to comment), the kata of aikido where uke (uke is teacher says nishioka sensei) provides the variability, stress testing through connection and randomness in free play.
A recent interesting example for me was at our national seminar where the application of happo waza (8 directions) was explored with multiple uke, it saw relatively experienced aikidoka tripping over their feet and not knowing which way to turn, this despite doing the happo waza 4 times a class, 2 times a week 50 weeks of the year, it was an interesting example of the traps of blocked learning.
I would see waza as a1st approximation of aiki, paired practice as examples of aiki that might allow one to discover aiki in time - get the odd glimpse.
hmm a few broard brush strokes and generalisations..apologies in advance