"I'll explain: Before you can launch Modern Warfare 3, you have to launch Modern Warfare 2 first. Seriously. "Call of Duty HQ" is just the Modern Warfare 2/Warzone client under a new name.
Switching between Modern Warfares 2 and 3 from the HQ is not like switching modes. Once you're on the main menu, you could jump immediately into Warzone or a multiplayer match of MW2. Clicking the Modern Warfare 3 button, however, closes the HQ app and launches an entirely different executable called Modern Warfare 3. There is no option to just launch Modern Warfare 3, because "Modern Warfare 3" is not its own game. It's buried, literally, inside CoD HQ as a piece of add-on content.
The result? It takes 70-90 seconds to launch Modern Warfare 3—at least, those are the times I'm getting. That's an eternity for CoD, but what's baffling is that these extra steps serve no discernable purpose for players. Perhaps Activision pitched the CoD HQ with consoles in mind, where games aren't so easily organized by series and an app that switches between the handful of still-active CoDs is useful."
Other way around, according to the article: the launcher considers it a mod for MWF 2 and as such it can only be launched by first entering the lobby of MWF2. It has no independently launchable executable file.
This is very wrong. They've been doing this with Warzone (which is free-to-play) for a while. If you try to launch MW2 from the launcher when you don't own it it just takes you to a page to buy it. There's no way they would lock you out of a game you own just because you don't own another game in the launcher. Not defending the practice though still completely ridiculous you have to launch the MW2 launcher first.
You can actually download it without buying . I wanted to play warzone on ps5 . Took forever to find the download for it but it basically makes you download all of modern warfare 2 just to play the free to play parts .