Why can't it aim to solve what it can do? TOR is a great example: the TOR network itself can't perfectly anonymize you due to browser fingerprinting, but users of the TOR Browser get both the TOR network resisting deanonymization on a network level and a browser with plenty of anti-fingerprinting measures built in. A VPN could aim to prevent deanonymization on a network level so that users who want to stay anonymous can use the VPN in combination with fingerprinting-resistant software.
The fact that Tor does not intend to tackle the timing problem is plainly stated on the Tor website.
If I'm on a public VPN, I don't want anyone to know who is making the request, including the terminating IP.
Think about it. By your logic, VPNs shouldn't be used for torrents because VPNs shouldn't anonymize you to the terminating IP. Whereas they work gangbusters for that.
If you are talking about private VPNs.. Mullvad isn't one.
But today’s internet is essentially a giant ad network.