Inspiration is earned by playing up certain specified character traits. A player chooses whether or not to play up those traits based on a range of considerations, of which earning Inspiration is one.Inspiration is earned by playing in-character, and it's an entirely in-character decision for someone to act in accordance with their own goals.
When the player then spends the Inspiration, what is happening in the gameworld? Are you positing that the world of 5e D&D is a type of fairy-tale land wear being true to yourself - even true to your flaws (whatever exactly that would mean) - makes you luckier?
Huh? It doesn't get more metagaming than playing up your PC traits to attract the GM's attention.Moreover, since it's only awarded by the DM, it's actually immune to meta-gaming.