Who's saying no?
Mavs get a couple young players who don't seem to fit into GS' future plans, draft capital and cap flexibility.
GS gets front court help, and an All-NBA(ish) caliber player to try to capitalize the last few years of Steph, plus a Draymond ish type of player in Naji.
Spurs gets veteran front court help for an immediate playoff run while keeping the bulk of their core and future assets in tact.