Plug reading useless

It's not as good an indicator as it used to be for pump gas, and of course differs depending on where you're at, but 'useless'? That's ridiculous.
I've noticed a difference though, in how the pump 91 we get out here the last few years reads. It just doesn't color up the insulators like it used to on a comparable tune.
O2 sensors are great but they don't tell you squat about timing, heat range, is there un-heard detonation..