I guess "strictly" is debatable, but the point here is that the market for at least somewhat browser agnostic services includes, well, the entirety of iOS at the least. Precisely because there is no "choice", which means big services/developers can't force a choice on us either. If I browse somewhere on my iPhone, I won't be told "go install Chrome" because a I can't (or rather, it'd make no difference because an iOS browser is still the same engine so like "iOS Firefox", "iOS Chrome" is mainly a skin). Sometimes I may see a "better in the app" which I don't mind if it's dismissible because if it's somewhere I actually like, well, maybe I really will try their app. And while iOS users aren't remotely the majority of the global market by user count, they tend to punch above their weight in spending; they aren't a random sample of the population. It's a not insignificant market to entirely forego.

Different people will have different services they depend on and different views of the web in turn, so YMMV, but at least for me that seems to have been enough. I completely uninstalled both Chrome and Chromium, and between Safari and Firefox on Mac and FF on FreeBSD or Ubuntu I haven't encountered anything critical that was non-functional. Apple has effective collectivized the buying power of a picky subset of people. That's definitely not always good, but nor is it always bad. I think at this point a lot of us are making a conscious choice to join that ecosystem, and those of us unhappy with some of it handle it by keeping our main computing environment mixed up.