While I share a similar opinion, the languages to be picked for a project should the official languages of a specific platform, meaning "Pick platform X", "X allows X, Y and Z languages on their official SDK/tooling", "X, Y and Z get the price of chosen languages for the project".

However I also think, that time should be spent in non-mainstream languages to learn new programming concepts, and eventually future version of "X, Y and Z" might even get those concepts and thus one is better prepared to apply them.