As a single hop proxy, VPNs are pretty limited in terms of the OPSEC they provide. Personally I only ever use them to route traffic over hostile networks, and spoof my geolocation to access geo-blocked content. That's all they should be used for[1]
They for obvious reasons should not be used for anonymity[2] although for some this is the sole reason they use a VPN. I think, since they are a single hop proxy, that chaining VPNs together and buying subscriptions anonymously with tumbled Bitcoins/Monero is the only way you might get anonymity, but the overhead and potential for things to go wrong is massive. Things like Tor already solves many of these obstacles and provides reasonable OPSEC, providing you use it correctly.