Modern Warfare 2's disc is basically an authentication key for a digital copy of the game.
It's been discovered that Call of Duty Modern Warfare's retail PS5 disc is nothing more than a physical installer with 72.23MB worth of files on it. Modern Warfare 2's Blu-ray disc does not include the actual game, and consumers will have to also download 130GB worth of files to experience the full game in its entirety, effectively making the disc itself redundant other than a gift or collectible.
This of course means Modern Warfare 2 can't be played without a day one update...except in this case, the day one update is the actual game. While this seems to be the case for modern Call of Duty games, it certainly isn't a widespread trend in gaming; According to Does it Play?, a tracking site that catalogs whether or not a physical game can be played day one without any sort of patch, 99% of disc-based games still do not require online downloads to play.
Luckily gamers can choose what to install. If you want to play campaign only, you can cancel the downloads of campaign packs, and vice-versa with multiplayer.
This isn't the first time Activision-Blizzard came under fire for this kind of thing. In a separate franchise, Tony Hawk's Pro Skater 5's game disc only included the tutorial level of the game and the rest of the actual game had to be downloaded separately.
Call of Duty is by far a digital-first gaming ecosystem where monetization, continual digital updates, and online engagement reign supreme...so this development isn't exactly surprising.