Approximately 16-18% of ActivsionBlizzard's profit last year came from "point-in-time" sales like the upfront cost of the game at launch. The other 82-84% comes from the "over-time and other" revenue which is the all time favorite microtransactions and subscriptions etc. (Source from their 2020 annual report, page 36)

Game sale records are great but having an active player base that's on and committed to playing through the games "life-cycle" to purchase all the crap in the game matters more than it did in the past.

I've found personally on PC, I can't find a game easily anymore in older CoD games, the matchmaking is essentially dead. On the other side of the coin you have BF4, BF1, & BFV, all with populated servers with decent ping for you to play on right now.

Three legacy CoD games (CoD 1, CoD: United Offensive, CoD2) are all $21.99 CDN for me right now on steam. But you can go buy Battlefield 4 right now with the DLC for around $6 on Steam or Origin.