This lack of ability to use common sense is an issue, but I have mixed feelings about this. In the US, the security screener position is generally viewed as an entry level, unskilled position.

In other countries (the UK, Germany, Canada, and the Channel Islands most recently) I see screeners locate and remove items larger than 100ml and/or not in a plastic bag. Generally they investigate the item, swab it, speak (politely) to the passenger, and in almost every case I have seen they allow the item to pass. (The exception I saw recently was at TXL with an older couple having ALL their LGAs full size in their luggage, but the screener kindly explained, arranged for LH to retrieve their checked bag, and found the wife a seat to wait for her husband while he checked those items)

However, the difference I sense is between professionals and generally unskilled labour which seems to lack the ability to follow even basic directives. I don't think that I would want TSOs to use their own judgement on those types of things as right now many of them fail at following the basics.