I so agree. But, single stage an be applied with lots of gloss.
I am no expert and having done more than a few does not make me an expert. But, I had several paint guys do cars for me back in the 80,90s mostly. One guy in particular, was a tremendous custom car guy. Unknown to most. He could do anything, body, paint, drivetrain, and he cold put down a case of beer a day. It was all single stage and he tried to explain to me a lot of it was using a very slow reducer, (today even slow hardner), humidity, and of course technique of pressure, tip, and laying it on. He could do single stage to revile any bc/cc.
But like you say, I too want it to look like back in the day even though our single stage paints today are better.