I typically play only unranked Historic Play.

Every time I delete a deck, any deck, the game automatically switches itself to Historic Ranked. Which I then often click without realizing because I was playing unranked games, or have to manually change back to unranked each time.

Not sure why this happens, whether it is a bug or intended feature. However, deleting a deck should not automatically switch which game mode you are playing.

I feel as if it has something to do with the "Recently Played" thing, but I typically only play Historic Ranked the day it resets. Then back to unranked Historic Play after that, and do not play ranked again until the next reset.

If the automatically switching game modes can not/will not be changed, and is affected by the recently played thing, then there should at least be a time limit to the recently played thing. Historic Ranked that was played a month ago is not so recently played.