I think many of the jobs which aren't completely automated, but could be automated based on a explicit reading of their job requirements, are due to many implicit requirements being part of the job.
For cashiers, beyond simply ringing up customers, they serve the function of:
1. Validating IDs
2. Preventing theft
3. Creating a positive atmosphere
4. Helping customers bag groceries
5. Resolving issues/questions about products/the store
For waiters, likewise they have the job of
1. Creating a positive atmosphere
2. Physically bringing food to the table and setting the meal
3. Upselling items, providing recommendations, catering to specific unusual guest needs
etc. Basically all these jobs have a huge soft-skills dependent interface which no technology currently can replicate what humans can do.
I don't think that every job can be trivially automated by a large language model, but any job where the inputs/outputs are entirely via a computer, LLM's are approaching the point where they are equivalently enabled to a human, and there is no "real human body in-person" soft-skills interface.
When I worked at Disney, there were some jobs where people's entire jobs were compiling reports and following up with various departments. Like taking lists of security vulnerabilities from scans and getting commitment dates to fix them. They would take the data out of one system and put it in a spreadsheet. Then they would reach out and create Jira tickets for the teams responsible and then schedule meetings if necessary to discuss. These roles are definitely at risk.