Synthetic Oil - good or bad?

I run synthetic oil in all my vehicles, including the 69 cuda, without any issues. I perform oil changes every 3k miles on vehicles out of warranty, and follow the factory periods while they are in warranty (usually 7k miles). Never had a problem with synthetic, the only thing with the barracuda is that I add zinc additive, even when it has roller-type rocker hydraulic lifts and rockers, but thats it. My engines have always shown clean and without lubricating issues whatsoever.

I think the engines get damaged when not given the proper regular maintenance, or if issues come up and are left unattended.