The bit when I said "conditions could easily warrant a join onto base or final" means when the circuit is quiet. I thought I'd made that clear, but obviously not.
For example; One bloke/lady just departing 28 (formerly 29), nobody else around, me coming in from Selby... so I could easily position for a straight in and land. Then I'd be off the runway by the time he called downwind, and if he's staying in the circuit I wouldn't be a factor.
If said bloke/lady is staying in the circuit, then surely me joining into the same circuit (crossing to the live side just as he's downwind in the worst case) could be a lot more dangerous than if I'd just landed while he was climbing out.
To force everyone into the same bit of airspace when it's busy doesn't seem too clever either.
Then you've got some people who turn crosswind early, others fly a NAVEX out to Garforth over about 10 track miles to position downwind, and others may be doing a bad weather circuit. Why add to the melee if you have the nous to just position onto a tight base or short final without affecting anyone else?
I don't think you can determine airmanship from circuit joining alone. Surely the better display of airmanship comes from somebody who can size up the situation they are presented with, and has the mental capacity to make a sensible decision based on that. Eg: No traffic, I'll join straight in.