I think people should view this trade like they viewed the AB trade. It's not exactly a swap for just raw talent, there were salary cap implications taken into consideration. Crowder and Zizic were salary filler as far as I'm concerned. Zicic won't be an integral part of a Celtics or Cavs title run, and this team has Tatum, Brown, Nader, Semi, etc. who can all fill the role of Jae Crowder. (And we all want to see the young guys develop).
The 2018 pick is compensation for the Cavs taking back a player that's injured, older, and expiring. The C's cashed in on 3 of the 4 Nets picks. Young, Brown and Tatum were drafted, and the last one was used to acquire a 25 year old 4x All-Star widely revered as a top 10 PG, arguably top 3 in the East, with a championship under his belt.
This trade was good for both sides.
Edit: Gave it a B