I understand that they weren't even planning on including Daeron in the show in the first place but, it was stupid to offhandedly mention him at the last second early in season 2 and then have nothing come of it from there. 

Two years and two trailers later we still don't see him (or atleast clearly). I understand this was done because it would otherwise make the "fake Daeron" plot redundant but it would've been so much better to not mention him at all in season 2, then have him appear in the second trailer of season 3 even if just for a second or two. It would have served as somewhat of a consolation to book-readers who thought they trashed the source material entirely.

I know why on-top of the fake Daeron plot that they're not showing him, and that's because from the split second half glimpse we get of him he appears to have dark hair and looks unremarkable and I doubt even Team Black are gonna agree that it was a good creative decision. But still.

They shouldn't have mentioned or alluded to him in season 2, they should have included him in the second trailer, either at the Greens' camps, or hopping off Tessarion, cleaning his sword, or anything else that indicates that there's a "new character" we will learn about in the new season.

\*This is just my take, to be fair. And I think it may be unpopular, but I said what I said\*

Unpopular opinion: it was stupid introducing him by name only in S2