Use your diary study to derive insights, rather than trying to get users to articulate desired outcomes. Sometimes user feedback is straightforward, and sometimes you have to dig into behavior a little more. Diary studies are great for this because they capture thoughts, feelings, and actions, rather than just opinions.
The famous milkshake story is used to educate about the role of identifying Jobs to Be Done. The important thing about that story was that when researchers asked consumers what they wanted in a milkshake:
They’d get very clear feedback and they’d improve the milkshake on
those dimensions and it had no impact on sales or profits whatsoever.
It was the unspoken actions (buying milkshakes before 8 in the morning, while driving) that helped researchers have a breakthrough moment in how to boost sales. Watch for any unusual behavioral details in the diary studies to see why users are "hiring" a product and "firing" others.