iCloud photo sharing

If you wish to view your wife's photos, then she will need to share them with you via -- How to share albums in Photos on your iPhone, iPad, and Mac - Apple Support. This is the only way to see each other's photos.

You are doing nothing wrong. iCloud Photos is not a shared feature of Family Sharing. You can have a shared Family Photo Album, that you can each post photos to, but you each have your own Photos when you use iCloud Photos and Family Sharing.

The idea behind Family Sharing is to share certain content like paid apps, music, movies, and books. You can also share a family calendar and family reminders, but Family Sharing still lets you keep your own data, files, contacts and other content private and that includes photos.

When you set up Family Sharing a shared photo album is created automatically. You can select photos that you want to share with your wife and then tap the Share icon (the square icon with the upward pointing arrow) and then select the option to Add to Shared Album>Family to place those photos in the shared album.