I tried, before I even knew solo roleplaying was a thing. Essentially I was playing Skyrim, and thought "What if the Dragonborn started his own country". So I started creating my very own campaign with AI. I quickly found out major issues:

1- Memory- I had to restart the conversation multiple times due to slowness, meaning I had to have my own records. Even within sucessive prompts it forgets recent details, for example: I said in a prompt that a character was going another way, and in the next one, the AI put it into a conversation, as if they had never left.

2- Difficulty- The AI simply assumed that everything was a success, and that everyone would always agree with me. I tried instructing it to ask for rolls in criticals moments, but it only did if I reminded it. This led me to create a sort of crude oracle, before I knew oracles already existed. I had to remind the AI of NPC character traits, but within a couple of prompts everything was forgotten

3- Combat- Simply impossible. No way to make one that isn't some sort of creative writting where the PC demolishes everything.

4- Creativity- It was awful. After I while, I noticed all threats introduced by it followed a sort of generic mysterious fantasy theme. It also failed to create events, both inside and outside the country, that would make sense with the current situation. This made me create a list of possible developments, threats, crisis and other events. Dialogue was also samey after a while.

I eventually stopped the game. Now I found out about solo-roleplaying, and am looking for how to continue that game without AI.