The first two issues -- a lack of index and the fact that you can't seek within a deflated tarball -- are true but are easily handled by smarter compression. Tarsnap, for example, splits off archive headers and stores them separately in order to speed up archive scanning.

The third issue -- lack of support for modern filesystem features -- is just plain wrong. Sure, the tar in 7th edition UNIX didn't support these, but modern tars support modern filesystem features.

The fourth issue -- general cruft -- is correct but irrelevant on modern tars since the problems caused by the cruft are eliminated via pax extension headers.