Don't worry, this is not a rant but a bit of a PSA.
A dev just said in a Twitch streams that those new decks are supposed to be unlockables through Reward Points so that new (as well as old) players can work on creating some good decks.
For some reason currently everyone that creates a new account is getting them, but that is not how it was intended and both new AND old players will be able to unlock them in the future.
I personaly assume this mess will probably be sortet out with the new expansion? All in all good news for us "old" new players tho.
Edit: Here is the link if anyone wants to watch the VOD, the deck talk is about 1 Hour into the video.