I think a lot of it comes down to game design is hard.
There's a lot of moving parts that go into it, and even experienced teams have difficulty finding the fun. It's extremely common that games that are now popular and beloved weren't very fun until a few months before they released.
> It's extremely common that games that are now popular and beloved weren't very fun until a few months before they released.
I'm not sure that's so common, most games released that weren't fun before they were all completely finish, don't fare so well in the end. What tends to do well, is stuff that is fun/feels good early on, but might not be "visually/creatively complete" until just a few weeks before launch. That last part, is extremely common in game development, maybe you got the two confused.