The lack of buttons for additional fingers also seems like an issue. Unless you use the awkward claw grip that I know some people did for certain PSP games, you

The lack of buttons for additional fingers also seems like an issue. Unless you use the awkward claw grip that I know some people did for certain PSP games, you're limited to just your thumbs for input. There's actually more controllers now than ever before that have even more buttons accessible to non-thumb fingers. A phone just seems like a poor choice for a game like Fortnite.