the 'dance club' 45's are all over the board in quality.....mostly bad.
I would agree that they are all over the board (so true of all recorded music whatever the media but especially pop....a real mixed bag).
However, I would point out that in comparison to the LP's produced at or around the same time, I often found the 45's sounded better than their LP counterpart...
Are dance club goers sensitivities less discerning of high quality sound reproduction than audiophiles?
I have to think about that one. Admittedly, I have not been to a club recently, but in younger days, when my hearing was at its very best, the top high end club systems in the big city (where you had to line up for hours as well as pay to get in)....well....their sound systems sure impressed me!
In fact this alone probably started me on the quest for a better home sound system as NONE of the big city audiophile stores came close in terms of exhilarating accuracy at high SPL's....I recall Blue Monday (New Order), Two Tribes (Frankie) and many other tracks that just blew me away....especially the accuracy in the hard to produce bass frequencies.
...and I don't mean boominess as top end clubs really had great gear...plus they had the advantage of packed crowds to absorb the longer reverberations. As Sabine put it...one person is roughly acoustically equivalent to 8 cushions in a lecture hall ;-)