My two cents:
You're absolutely right. GGT was banned to weaken, but not completely destroy Dredge. Then, shortly after, they changed their minds and decided that they'd rather just kill Dredge completely, and banned Dread Return
There is absolutely no reason for it to still be banned, because Legacy Dredge cannot port-over into Modern at all without Dread Return
. However, Dredge is one of the most universally hated decks in existence, and unbanning GGT would be suggesting that they actually like
Dredge, which would not go over well.
Don't hold your breath.