Starting from 1 Nov 2022, apps that don’t target an API level within two years of the latest Android release (API 29 and below) won’t be available to new users with devices running Android versions newer than your app’s target API level. This means that new users won’t be able to discover or install your app on Google Play
So if the app is older than 2 years… and hasn’t been updated to say it supports the API level your phone is on, it will not appear available for you in the play store. Most of the time, the APK still works fine… The app developer just doesn’t support the app anymore and thus hasn’t updated the arbitrary checkbox for the playstore. On one hand, if it still shows up in the play store you know the app dev is at least “around”… On the other hand… it doesn’t make sense to keep updating an app that doesn’t need updates.