I think because of the many problems listed and the significant one you add (Just what is a breaking change? It turns out pretty much any change can be breaking

I think because of the many problems listed and the significant one you add (Just what is a breaking change? It turns out pretty much any change can be breaking for some user), the tooling needs to recognise that strict semver is unsound and a looser version is required. This isn't just a question of pesky humans with their marketing versions vs unerring machines - there are complexities in the problem space which shouldn't be ignored. Different producers/projects have different expectations for strictness in semver, and that's ok, they can use it differently in a negotiation with their consumers. Also different consumers have different requirements, and most tools provide a way for them to specify that on a per-import basis (upgrade only minor of these pls unattended, upgrade nothing on this one, only breaking changes on that one). In short, loose semver is a feature, not a bug.