Good portions of standardized learning will be a waste of time for any particular person: It’s a standardized path, therefore, it has limitations in how much context (experiences, goals, etc) they can considered.
Some of them are better than others to encompass context.
E.g., I have studied for PMI’s ACP certification. Are many things there basically classroom fables? Yes. Are many things there oversimplifications? Yes. Was it a complete waste of time? No: I was exposed to the iceberg tip of many interesting topics; if I felt that I end up in a real-life situation that it’s similar to the book, I could go there for some initial guidance, instead of having to fight the lion without a clue.
My understanding is that ISTQB Foundation never claimed to be able to prepare a professional and it got much bad rap because companies put it in their job requirements. It’s unfortunate, but IT HR is full of oversimplifications as well, part due HR people and (good) part due IT people - Bob Martin always opens his talk speaking of how we could do better in explaining (and practicing) excellence: You don’t need to be a doctor to at least shallowly understand what makes good medical practice.