I'm happy that MWIII exists since it looks like Sledgehammer Games tried their damnest to overcorrect what went wrong with MWII's multiplayer. (If IW had full reign on MWII.) Weapon unlocks, cumbersome UI, perk progression, underutilized extraction mode, marketing on nostalgia. That said, since the majority of MWII carries over to MWII (weapons, maps, not sure about progression), MWIII's existence invalidates MWII as it's a copy/paste that feels like a substantial update similar to No Man's Sky.
I wish I would've played MWIII to unlock Laswell before she was locked behind a paywall now...