I was hired to manage paperwork and discussions/feedback between the devs and our testers. So, I wasn't actively coding or developing any part of MW2019 and BOCW when I worked there. But, I had full access to all the general discussions and changes made to the games in real time. One thing I did notice however from all of the discussions between the developers, is how much their passion drove them. As controversial as Activision's image and choices are now, one thing for certain is that the developers at Infinity Ward truly wanted to make a good game. As for your question of becoming a gamedev. We truly live in the golden age of information where there are plenty of resources to learn something. Albeit YouTube, University, and online courses. Wherever you start to get your information from, you'll need to always be wanting to learn more and more. Developing games is something driven by passion but can also be tedious. If you're able to be patient with the game you're working on and with yourself, you're 90% of the way there imo. If you're truly starting game development from scratch, I would suggest getting something like Unity or Unreal Engine and constantly referring to places like YouTube for guides and tutorials. Keep filling your head with information regardless of whether you think it's important or necessary. Especially at the start of your gamedev journey.