Confusing contact photo and poster system on iPhone

I literally can't wrap my head around it and it seems like something a 5 year old should be able to do. If you click your Apple ID from phone settings, then click the circle, it lets you choose from a bunch of random icons or your initials in 4 random colors they choose, or upload a photo. So I upload a photo of myself, so now it shows my profile picture with my Apple ID. Now I go to my contacts, and in my contacts, the icon shown for my contact card is still showing my initials. So then I click "contact photo and poster" on my contact card, and it shows a bunch of poster layouts, none of which have the picture that I set up in Apple ID settings. So then I go back to my contact card and click "edit" in the top right, and it brings me to a page with a circle with my initials where the picture is supposed to be, so I click it thinking this must be where can upload the picture, even though I already did that in Apple ID settings. Then it brings me to a screen to choose a poster, not a profile photo; and this time literally a completely different poster selector screen from the one in the Contact Photo and Poster; this one with the options to choose camera, a photo, a Memoji, and monogram. And guess what? Clicking on photos lets you import a photo to put as a poster background, not a profile photo.

Who created this? Where can I just change my profile photo that my contacts will see??? Should this be so difficult?

[Re-Titled by Moderator]

Original Title: Can someone please explain the contact photo/poster system very clearly? Because it makes absolutely no sense