That’s fair to point out, but it implies the only utility users provide to the site is ad impressions. I see a couple of reasons this is not the case.

Mods make up a tiny portion of users but are disproportionately 3rd party app users and rely on 3rd party tools. But if any meaningful portion of the mod community leaves? The remainder were going to have a much bigger job without the tools. To attempt the bigger job with a smaller workforce is a double-whammy. Their only option will be to focus on their favorite subs and elevate more members to mods. The inevitable result will be experienced mods being far outnumbered by new mods, all of whom will have to stick to tedious tasks for subs to not be overrun by spam and hate speech. It’s hard not to predict the same result as what’s happened to Twitter’s content.

Now consider nsfw content, which has always made up a huge chunk of reddit’s traffic. Moderation is even more difficult there to begin with and could easily melt down for the same reasons, even setting aside reddit’s growing distaste for it. Reddit is largely young and male and while many users may have no interest in it, the combination of nsfw imgur links going dead, moderation challenges, and the likelihood of reddit cracking down on nsfw is a combination that may cause reddit to be less attractive for many of the young, male userbase to visit.

I think your point still has merit - reddit won’t miss many of the users seeking alternatives. I would say reddit’s casual “I didn’t even know there were 3rd party apps / old.reddit.com” users are also likely to be turned off by the ultimate results of their changes.