The truth about VPNs? - Divisions by zero

So I’m pretty recent to the high seas but I’ve seen a few posts now about “stop relying on your VPN” and “people that think VPNs will protect them are naive” and so on. So since I believe knowledge is our greatest weapon/tool/super-power, can we get some answers regarding what exactly the doomsayers are getting at? ELI5 why VPNs wouldn’t protect your anonymity. Is it about logging? The country your end-point is in? Something more technical? Ultimately I’d like to be fully armed in order to keep making the best choices for my fledgling ship as it navigates the vast, stormy seas.

VPN is good as long as you use it correctly. I've seen people use vpn and still loging into there email or bank or do shopping while on same vpn that they use for piracy. Number one rule when using vpn is to never mix your real life accounts with the onces you use with vpn.
Well, your VPN knows your address so this advice is pointless. Unless you only access your VPN through a totally anonymous ISP at a totally random location on the planet each time, probably impossible due to KYC laws, you are certainly not anonymous.
For piracy purposes its irrelevant. The VPN provider won't send you a complaint or give your details to a copyright troll. If you are hiding from the governement then maybe its a different story, but a copyright holder doesn't have the ability to force a VPN to do anything.