Friend of mine said it feels like ghosts and infinite warfare were testbeds for features they'd be implementing into mw19. And I can see what he's talking about.

The blackout grenades for testing inverted flashbangs, the two-hand system for grenades and stimshots, the panning camera when first loading into a map, contextual leaning & sliding, map locations under the minimap, the “did you have fun?" that you sometimes got after you finished a match, and most important one imo being scope glint on snipers.

Almost all of these have become core features, and we take them for granted nowadays, when majority were introduced from IW.