In practice there are problems: Everything can throw IOException technically which you need to handle. There are non checked exception anyway, so there might be exception that are thrown anyway. It's a mess and there is a reason no other mainstream language uses them, even if Java people don't like that fact.

A lot of that comes back to the lack of power in the type system (type erasure, lack of union types, etc).

If all that code throwing IOException could express better the type of fault, and if the error handling could them in a more nuanced, less awkward manner, it would be much better than it is.

"Everything can throw IOException technically which you need to handle"

wut?