While I'm not a native Japanese speaker, I've lived here for a decade and communicate in Japanese 98% of the time at work.

"Ikigai" is just a combination of "ikiru" (live) and "kai" (worth doing). The existence of such a word does not imply any more of a coherent or commonly followed philosophy than the existence of the English phrase "purpose in life" or the loanword "raison d’être" does. Pretty much everything I've seen about the "unique Japanese concept of ikigai" appears to be almost entirely made up by non-Japanese people.

Not that it's necessarily a bad or useless concept, but claiming this particular formulation of it is ancient Japanese wisdom appears to be a marketing effort.