My experience is that people who think that never worked with a language where inference is principal and complete (aka, "good") and/or have poor editor support

My experience is that people who think that never worked with a language where inference is principal and complete (aka, "good") and/or have poor editor support. In languages that are still reasonably close to HM and that have decent editor tooling, like OCaml, leaving the type out in the implementation is the common practice. You only write them down in the external API (along with the documentation).