We’re going to have plugin dependencies - we need that to make core plugins work; we can mark plugins as unmaintained, we can stop tracking them for new major CP versions, we can flag them as “author doesn’t respond to security issues”, we can even hide them from certain searches - the only thing we cannot do is delete them. We all remember the npm debacle, yes?
Using semver means plugin compatibility will be tied to major versions, which makes the directory effectively self cleaning. If the author doesn’t update the plugin meta for the next major CP version it won’t be listed - simple as that.
The assumption in the WP repo is that plugins that work with e.g. the last release of v3 will work with the first release of v4. Our assumption is the opposite; because we know there will be breaking changes between e.g. v2 and v3, we cannot assume plugins will carry on working.
So, to address the title of this thread directly: no, but they should be appropriately flagged.