Well, this doesn't exactly replace that entirely. The LGBT+ rainbow is supposed to be for everyone who falls into that larger group, but I see no harm with there being individual color combinations for specific sexual orientations and gender identities -- especially for groups that fall into the "+" and are therefore less likely to be represented/recognized.
And if we're just talking from an artistic standpoint, I've actually seen people point out that all the specific color flags are in lighter pastel colors, making the overall rainbow a bit harsher on the eyes in comparison, and so people are saying that a pastel rainbow would look nicer. And, speaking purely from an artistic stance, that actually makes a lot of sense. XD