Don't agree with the point. Good stories originally expressed in one medium - whether a novel, a live-action film, an animation, a musical, an opera, a drama play, a television show, a comic-book, a graphic arts novel, a song, a theme park attraction - are often re-expressed or re-told again and again by others in different mediums. Rather than devaluing the previous mediums, it can introduce new audiences to the how the story was previously expressed in a different medium and create new found appreciation for it.
Plus, if the author's point were correct, wouldn't we be seeing fewer animated movies and less talent providing the voice-work? It seems to me that we are seeing more stories being told in animation than in recent years than in the past, and it's not limited to Disney and Pixar. In addition to Inside Out, Frozen, Big Hero 6, Zootopia, Moana, etc., there has been Sing, Secret Life of Pets, Boxtrolls, Despicable Me and Minions, Home, the LEGO Movie, the Hotel Transylvania movies, etc.
There's a fair amount to criticize regarding the live-action remakes - whether Disney is going too far and doing too many; whether a particular remake is too much like the original or bastardizes the original, whether the particular remake is an appropriate fit for live-action (Dumbo??); the quality of the execution and performance; etc. But I disagree with a wholesale condemnation of the practice as inappropriate and wrong because it purportedly devalues the animation medium.