what I'm doing wrong
well obviously with all your cacti you are doing many things right to have so many flowers 🙂
I think my favorite is the Hatiora gaertneri aka Easter cactus. The flowers are pretty and I like the way they kind of cascade down.
I'm rather partial to that one too. These guys are a little tricky for me, it's often too hot and sunny for them. Some plants also only root at particular times of the year.
Cavcti flower if they grow outside, they really need to feel the seasons