My guy has a tongue ring. He's had it for about 15 years, no problems with his teeth because of it.
I had one for 9 years and only took it out because I was tired of it, not because it was giving me any funky taste or harming my teeth.
I also have a labret and have had it for 8 years.
The main thing with mouth jewelry is to be sure it is sized to fit where you're wearing it.
The barbell in my tongue was small enough it never hit my teeth unless I intentionally clacked it against them.
My labret sits flush against my inner lower lip (low) and never hits my gums or teeth.
I think calling it a generational thing is...
Well, let's just say I got mine (tongue ring) when I was 30 so I certainly wasn't some young punk. I'm now 41 and have no intention of getting rid of the labret.
Also, surgical steel rarely gives off a metallic taste or any taste at all.
Back to the poll, though...
While I love piercings of almost any kind, I have NOT found tongue piercings to make a difference with oral sex. If anything they get in the way of hard thrusting into the mouth and across the tongue.