Comment by owaty

I think the GP has the following causal diagram in mind:

               +---------------------+
               | Author's competence |
               +-------+-----+-------+
                       |     |
                       |     |
    +--------------+   |     |   +---------+
    |Implementation| <-+     +-> |Product  |
    |  language    |             |language |
    +--------------+             +----+----+
                                      |
                                 +----v----+
                                 |Language |
                                 |quality  |
                                 +---------+

So you are both right; language quality is a function of the language itself, but if we don't yet know much about the language or its author, there is a correlation ("confounding") between language quality and the choice of the implementation language, so if that's the only information we have, might as well take advantage of it.

I am not weighing in here on what specifically the choice of Haskell, OCaml, or Go say about author's competence; I am simply addressing your point that the choice shouldn't matter at all—unless you are convinced that the knowledge of PL theory and design principles is uniformly distributed across all language communities.