> meant to have good ratios and good (de)compression speeds as compared to other tools

That does not mean it's Pareto optimal; Pareto-optimality forms a curve and while zstd, LZMA, LZ4, ZPAQ all want to be as close as possible to the curve, they focus on different parts of it. In particular zstd tries to stay on the middle part of the curve, while LZMA and LZ4 focus on opposite sides

          ___.--- higher throughput
        /     LZ4
       / zStd
      |
      ; LZMA
     |
     | ZPAQ
    lower size

Also, the Pareto curve is not necessarily known in advance. All you can do is add more and more algorithms or tweaks to understand what it looks like. For example, this blog post [https://insanity.industries/post/pareto-optimal-compression/] shows that prior to zstd, bzip2 and gzip2 were both pretty much Pareto optimal in the same area for ratio vs. compression speed. LZMA at low settings was a bit better but much slower. There was a huge gap between LZMA and LZ4, and bzip2/gzip filled it as best as they could.

The same blog post shows that zstd is an absolute speed demon at decompression; while not all zstd settings are Pareto optimal when looking at size vs compression speed (in particular LZMA wins at higher compression ratios, and even considering zstd only there's hardly a reason to use levels 11-15), zstd is pretty much Pareto optimal at all settings when looking at size vs. decompression speed. On the other hand at intermediate settings zstd is faster and produces smaller files than gzip, which therefore is not Pareto optimal (anymore).