I am annoyed by the early days, when some people still play fully optimalized decks from previous expansions to abuse people trying to experiment.
Maybe it would be great for first 1-3 days have requirement for standard (or unranked), that standard/unranked decks need to include 5(10) cards from new expansions, so people actually need to play new cards.
This way the first few days would be superexciting, people would be experimenting with cards while not being abused by people playing optimized version of previous expansion (plague DK).
stop trying to put artificial limitations on standard.
due to power creep, new cards are already stronger than old cards. Old decks are fine for familiarity for the first month or so but already fade out of relevance most of the time as time goes on.