I'm going to take a wild guess that you're going off of experience from something like npm library versions. That ecosystem is a mess, and I don't blame you for mistrusting it.
On the other hand, the Go language has maintained the Go Compatibility Promise remarkably well. https://go.dev/doc/go1compat
In other words, whether or no semver is useful depends on how well its followed. The versioning compatibility would be a problem regardless of the version number system followed. Case in point: Windows 95 v Windows 10.
I'm going to take a wild guess that you're going off of experience from something like npm library versions. That ecosystem is a mess, and I don't blame you for mistrusting it.
On the other hand, the Go language has maintained the Go Compatibility Promise remarkably well. https://go.dev/doc/go1compat
In other words, whether or no semver is useful depends on how well its followed. The versioning compatibility would be a problem regardless of the version number system followed. Case in point: Windows 95 v Windows 10.