Why?
Let’s talk about it in 2 parts, and after which should you understand why I refund my MWIII VAULT EDITION.
The creation and implement of SBMM will totally ruin your gaming experience.

Blueprints are fancy, while they cost dollars. Not paying means defeat, PAY 2 WIN.

Immense bugs and server problems. Some of which still not be fixed after 1 whole year

Boring events, the existence of these events and cobrand are to sell their own packs for your money

Some jump-scares are inevitable during events, what if the player has heart disease?

Not only P2W, gamepad plus paying means UNSTOPPABLE!

The emergence of kV and dragon-flame makes every battle sucks(especially shipment)

Ugly UI ‘design’, no better than that of Disney+ on PS5

Endless crashes make it a real trash

Cater to noob players, motility set a ceiling that is hard to break.

After every tiny update, Optimizing shaders will always wait there just like your puppy.
For more, other reviews are worth a read

Allow me to refer some IGN editor words here, MWII&MWIII's campaign is shallow, dull, and plays less like the greatest hits and more like underbaked cover versions of missions past. It’s too busy looking back at former glories rather than focusing on making any new moments worth remembering, wrapped up in a borderline incoherent story with nothing to say. The only part we haven’t seen in a campaign before falls flat, bizarrely cobbling together pieces of the Warzone mode into actively bad sandbox missions, abandoning all of what made Call of Duty so great at its peak and instead delivering a dull string of missions that amount to a thoroughly disappointing handful of hours.