my opinion is a good language needs these qualities. Portable, Safe, Fast, Easy.
which seems to be similar to the author of the article. the language I have found to match the criteria the most is the D programming Language, its so mediocre in every area.
3 separate compilers, gcc llvm and mars backends. can be as safe as you want it to be, with constructs for purity, GC, and contracts built in. can be as fast as you want it to be it is a systems language and gives you all the necessary tools to go down to C level or below with a good in line assembly, but generally the idiomatic code is fast enough you dont need to go to the C level.
it is also very easy, you have a lot of C libraries and D libraries you can use and with a built in C compiler (currently beta) you can import C libraries easier, it also has a similar syntax to C so its very easy to rewrite C code in D, it has an optional GC so if you are going for max performance you can beta test algorithms quickly using the GC and when you are ready for max performance you can do it all manually, or you can use the feature to test what is using the GC so you can avoid the GC in loops, I did this in a game recently, I used the GC to setup all memory at the beginning and turned off the GC so I would never use it in a loop,
another nice feature is functional features that make the language cleaner to write. I dont think this approach of being perfectly mediocre is necessarily the best but at least on paper its very good, and in practice there have been companies (specifically Weka Digital) that swear by the approach, they can use one language for both testing out ideas and the final product. but again in a lot of cases you dont want a language that is good at everything you want one that is good for your use case.
also the article was very interesting, language design fascinates me and the article was a good read really enjoyed it. currently planning on learning Haskell and Zig soon should be fun to compare these once I am comfortable with them.