Eh, WotC is a company and they offer a product(DDB)... they, like any other well run business, offer perks to those who choose to patronize their product. I think DDB is a game changing tool that offers immense value (especially in allowing the sharing of sourcebooks) to me and my group...if offering those exclusives allows my favorite edition... 5e... and its tools to continue and even grow, I have no problem with it.
Here's a parallel example, there are certain ttrpg creators who only offer certain products via their patreon....is that bad for their game?