App Store opening instead of the app itself

when I click Instagram link on WhatsApp, it just opens the link to the Instagram post in Safari, showing only.

When I click “Instagram is better in the app” with a button that literally says “Open the Instagram app”.

When I click THAT button, it instead opens the App Store page for Instagram, which is already installed.

When I click the “Open” button, it finally opens Instagram, but doesn’t redirect to the post or comments I was trying to view in the first place.

It’s not just Instagram. If open a Reddit link in Safari or Google, I’m prompted to view in the Reddit app, but it just redirects me to the App Store even though the app is already installed.

Am I doing something wrong? Did something change in my settings? Did an update screw something up? I refuse to believe this is by design - it’s too stupid.