The main “bad thing” about OCaml is it’s tremendously and strangely unhandy cross-platformness. The big surprise for me was the extreme clumsiness of Windows port (and the whole language looks a little clumsy in some parts, but it’s not so bad).
The post is just another one “static vs dynamic” review. It is not quite right to compare OCaml and Python, each language has it’s own field and all of these “high gains” may be just a result of choosing an inappropriate tool for the first time.
IMO, the Ocaml language has some weird cases, but in total it’s one of the better designed languages as a whole. It’s small, fairly consistent, and adopts useful ideas.
I think you might be missing the overall point of the post. My interpretation is that the point is that the two languages are comparable. They have roughly the same niche, and this is a list of what you gain when you use Ocaml to solve your problem where you could use Python.