Yes it does while the Witcher only has to satisfy just a SP mode, COD satisfy everything.  From SP to MP to CO OP you get everything in one package.  Just because a SP takes a while to finish doesn't mean the amount of content in it has anything to do with the file size.  You are equating 2 different things.

Supporting co-op or what have you shouldn't really increase file size much, it's more the amount of assets, voice lines, cinematics, etc.

Even back on PS4/XBO COD games were like double the size of Witcher 3 which is absurd given that game has a massive and detailed world with high fidelity assets, hundreds of hours of voice lines and cutscenes, etc. 

File size isn't a fixed thing either, it can be reduced in various ways; on Switch 1 many PS4/XBO games were reduced to a fraction of their size when being ported to Switch, the same could be done with COD.

Supporting CO-OP in a completely different map like zombies does increase the file size.  

Stating the switch when you can see a huge difference in texture quality doesn't actually support your point.  If anything it just proves that the quality of your assets are the issue. Why would COD drop the quality of their assets when the hardware its made for can display those assets at acceptable framerates.  There are few games that consistently have high frame rates and high assets like COD.  The thing is, COD has high file size because all of their assets are high. There is a particular quality level every COD player expects, dropping that quality isn't going to make your player base happy for the few people who do not play your game.

There is 2 things that seems to be a constant with COD, one is that its usually one of if not the best looking FPS that consistently runs at a high framerate on all platforms.  

Zombies is playable in single player or co-op, with the same maps, so adding co-op shouldn't have any significant size cost; the mode does, but COD is hardly the only game with multiple modes, many smaller games do it.

And that's the thing, there are better looking games with less file size.

How many maps does a COD game even have? Are those maps really bigger and more detailed than what you'd find in other high end games? I'd argue no, not really.

As for downgrading the graphics, the kind of gamers who play on lower spec systems won't care if it doesn't look like the PS5/PC/XBS version, those who do care aren't the target audience for such a port so what they think is irrelevant.

Jez Corden (XBox insider) says Call of Duty will launch on the Switch 2 in a few months time, the port is almost finished. They didn't get dev kits in time to launch day and date with the other versions according to him.

You evidently have not played the zombie mode if you are saying they are the same map as the SP of the COD campaign.  Yes you can play the zombies mode SP or CO-OP but it is its own game in itself.  

What better looking first person game that runs at 60fps consistently that look better than COD. 

COD has 16 maps for this version of various sizes.  While you will argue no the maps are not bigger or more detailed than you will find in other high end game its evident you have no clue as its evident you do not play COD.  Cannot argue a point if you actually do not have any knowledge of it.

Lol, there is only so much you can downgrade before it looks like crap and saying no one cares is more like you saying you do not care than anything else.  Sales is always an indicator if people care so when the sales are not there well something is the problem.

I didn't say it was the same as the campaign, but zombies or the campaign are basically the same whether you play them single player or in co-op, so co-op itself does not add to file size in any significant way. A side mode like zombies is not a game unto itself, games have had side modes for decades without taking up hundreds of gigabytes.

As mentioned, even back when this problem started, Witcher 3 was like half the size of the same year's Black Ops 3 while having better graphics and more content, and the same year also saw Star Wars Battlefront look much better and take up less space. And that before the file sizes got as bad as they are now, it's only gotten worse since. A big file size is understandable to an extent, but to this degree? I don't buy it.

Switch 2 owners will obviously not be bothered by their games looking like Switch 2 games rather than PS5 games, they knew when they bought their system that it was not a high spec console. And there's no evidence that the "sales are not there" at this point as it hasn't been tried yet.

Zombies and the campaign isn't even close to being the same.  At this point I am not even sure you even know the difference between the 2 different modes.  They are totally different and separate games with totally different maps and environments.

Witcher 3 really isn't the comparisons you want to keep using.  Use another Frist person shooter that has SP, MP and a separate CO-OP campaign.  We are not talking apples to apples here.  Even still, would you even know what is the size of the campaign compared to the size of MP and then the size of the Zombie mode.  You do know that COD has allowed you to install those separately for a while now.

You keep talking about switch 2 owners like they are some monolithic group, instead just say you because all switch owners are not the same.  I could easily say that Switch 2 owners have no interest in COD because that isn't what sell the on platform and the people who would purchase COD on Switch are people who already buy COD on the other platforms and would not want a crapy looking port.  

I'm not saying zombies and the campaign are the same.

And I'm aware they're installed separately; personally I'm not interested in the multiplayer stuff, but a lot of people are and so are stuck with enormous file sizes.

COD hasn't released on Switch/2 so there's no evidence at this stage that owners would have "no interest in COD". A lot of Switch 2 owners don't have a PS5/PC/Xbox Series. You also don't know that it would look "crappy", the port could turn out competent.

As I stated, you can just install the MP and not the other modes at all.  You have been able to do this for about 5 years now.  I just checked COD 7 today.  You can still just install the mode you want to play so no you do not get stuck with enormous file sizes.

Exactly my point, we have no clue what switch owners would want in a COD on switch so why keep saying that switch owners do not care about this or that when we actually do not know.  Switch owner are not monolithic.  Also I did not say the port will look crappy, I said if the port looked crappy would a switch owner want it.  That is a huge difference.