I use instagram because several of my friends are amazing photographers and I like their photo diary uploads, others are graphic artists who often release their work in progress on the platform. I quit facebook because it stopped serving any useful purpose to how I consume content from actual friends and in general became rather boring.

Is this an equally dumbfounding use?

No, your scenario suggests you migrated platforms because one stopped being useful and one was more useful, which is just a clear example of network effects, and sensible.

It would be silly if your reason for quitting FB was because you were opposed to them, and then you ran onto IG anyway. Sort of silly when that happens.

Fair enough. I was just wondering where the lines of nuance were being drawn.

I have a niece who posts photos more to Instagram than to the family group chat (2/3 iPhone, 1/3 Android).

I don't have any Facebook apps on my phone, tablet, or computer. I use Instagram and Facebook with Firefox with them locked to a Facebook container. For Instagram, I use User/Agent Switcher to tell it that I'm on an iPad using Safari. It works well except that Facebook won't let me set up two-factor authentication and asks me every time to download the app.

Every once in a while Facebook asks me to join the Facebook and Instagram accounts and I refuse to do so. I assume that they're combining the data anyway. But Facebook does let me use a security key as 2FA and I don't want to lose that.

The major downside is that I can't post to Instagram. But that would bother me more if I were a better photographer or my kids were younger than teenagers.

I also use Fluff-Busting Purity (formerly Facebook Purity) and two kinds of ad-blockers (AdGuard DNS on the router, uBlock Origin in the browser).

I mean, they're different products. There are good reasons for quitting the Facebook social network product which are separate from reasons for quitting all Facebook-owned products.