Help needed. Google is failing me.

I have an A53, running Android 13. I've recently noticed that if I uninstall an app and the reinstall it, it still has login credentials. That leads me to believe that uninstall isn't really deleting all the associated data.

How do I truly purge all the data from these apps from my phone?

I tried to Google the issue, but all the answers wanted me to download additional software, which seems antithetical to my goal.

(Please keep it simple; I'm not so good with tech.)