While Meta Platforms Inc. is investing billions in improving and accelerating the development of artificial intelligence, the most comprehensive showcase of its efforts — the Meta AI app — is an under-personalized and inconsistent experience, showing how far the company has to go in order to meet or exceed what rivals already offer.The app, which debuted in April, was both a latecomer and unique enough to be its own thing. As a standalone application, it arrived almost two and a half years after...