It surprises me that COD isn't on the Switch when it was on mobile, DS & Wii. The argument some people bring up is that "the Switch can't handle it". However, we've seen one of the biggest most graphically demanding games this gen like the Witcher 3 make there way on Switch, which imo is more demanding than COD MW.
I hope most people understand this, but I'll point it out here.
Switch can essentially handle any game. It's a matter of how much money a publisher needs to, and wants to, spend in order to make it work with acceptable results. So when people say "I don't think Switch can handle it", that can be a shorter way of saying they think its unfeasible considering the cost, and/or that the end result may stray too far from what the publisher thinks is acceptable for their title, etc.
Witcher 3 does not mean that any game that is less demanding has no excuse of being ported to Switch. Rather, it's a case study of how well they were able to make a game like that run on Switch. And even on just one cartridge.
But the relevance to your question here is that CD Project Red were willing to spend the money to make this happen.
Not every publisher sees it that way, even for games where they potentially need to spend significantly less money than CD Project Red did.