Interesting discussion...
My remark was prompted by the thought that the purposes of the ATZ are, in Law, divorced from issues to do with the pattern of traffic at an aerodrome.
Rule 17 (5) tells you what to do 'in the vicinity of an aerodrome', Rule 39 imposes requirements for flight within an ATZ. The two are distinct.
So, I would suggest that when joining the circuit, one simply assesses the 'pattern of traffic' and coforms to it. It may be a large or small pattern, depending on lots of factors.
Of course, this pattern size argument will run and run as it has for years. I tend to fly a circuit suitable for the day, so, a circuit in a B737 in great weather may have the downwind leg five miles from the runway, whilst in a C152, in poor visibility, I may be over the parallel taxiway...
As to more aircraft making the circuit bigger, this will happen, quite naturally, and when things quieten down, it will contract again.
One thing I do have a personal problem with, is using a 3deg glideslope in a single. This puts you outside gliding range of the runway, and is, IMHO, bad airmanship. Mind you, the same can be said of flying rectangular circuits so beloved of the GA community, rather than oval circuits beloved of the military or cropped circuits, popular in the gliding world.
ps 'complaining' to ATC may not achieve much - they don't dictate the pattern size. If you have a real beef, you might approach the CFI...