All good points. I was 19 at the time, and the spacers/adapters were installed at the tire shop where I bought the 4.5" bolt pattern mag wheels. Nobody told me about retorquing them, and back then I knew no better.
Hey I’ve done the same. I know better now, but I certainly haven’t always.
My point is only that people blame the spacers, but, I would bet in a lot of those cases the spacers weren’t to blame as much as maintenance.
It’s definitely a consideration, with the spacer/adaptors you’ve got twice as many lug nuts to maintain torque on. More parts means more things to go wrong. But all things being equal, the spacers are safe if properly maintained even if it’s more work to do that.