On my desk right now there are five Android phones (two of them don't even have SIM cards). I use them for different things. I wouldn't dream of signing in to all of them with the same Google account.
If you want to retain some degree of privacy and use Instagram on your phone, you need to get another phone for that.
They're cheap.
Second, phones are a terrible platform for privacy preserving technologies, both currently (mobile OS dumpster fire) and intrinsically (lower resources, poor input, well-known network identity). Anybody who cares about digital privacy should have a real computer laptop/desktop that they use for the bulk of their activities.
Not being locked-in into apps is critical nowadays.
Someone earlier astutely stated the metaphor “the thin edge of the wedge”; the movement to the “cloud” via the open web over the last decade was the thinnest part of the wedge.
Even to the extent web is open today, I’m able to run Linux on all my PCs/laptops and not to have an extra one to run proprietary OS in order to participate in modern life.