The conclusion is not radical but quite banal. For some data, zstd (and lzma) lose to methods more suitable to that kind of data. For example, for text, use ppmd.
Using bzip2 is not a great idea because it's old, you can always beat it using newer methods. But bzip2 is widely installed, so that makes it somewhat useful.
The OP also shows zstd being very close to lzma for high compression ratio jobs. In my experience, for higher compression ratios lzma handily beats zstd (in the pareto-optimal sense of the word). But lzma is slow to decompress. If decompression speed matters a lot, zstd is awesome.
If you need to compress something like game assets (compression speed doesn't matter, compression ratio matters, decompression speed matters a lot) and can afford to use proprietary code then check out Oodle [1]. It beats zstd.
