What are the known lessons of launching MVP too raw or too early?

Like this question — I post it at the moment it emerged, and seems like it's sufficient and clear.

But lacking example or explanation of what I mean it can either be missed or, what worser, can get downvotes.

I mean digital startups/MVPs, but I think insights may come from any area.

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edit: didn't expect to be downvoted here
edit: thank you kind stranger for pulling me out from that down