I always find this particularly apparent with open-source games, as there's hardly any rules for how to implement those. Usually you want games to be fun. Maybe you can agree on a genre. But from there onwards, most decisions are rather arbitrary and often decided based on gut feeling, which makes them difficult to discuss.

Commercial titles do struggle with that, too. That's why there's a bazillion Call Of Duty parts, each with merely incremental changes.
But on the open-source side of things, it often feels like for each game with a unique design, there's a dozen copies/reimplementations of commercial titles.