0% max block size is 4mb since 2017.

There is no size increase for the total transaction (still 100k vbytes), and so there is no size increase to the inputs. The change is changing how much data in the op_return part of the transaction nodes will relay. The change means your op_return data can take up the entire 100k vbytes and core 30 nodes will still relay it by default. Prior to core 30 nodes would only relay transactions with a max of 80 bytes op_return data by default. The change basically means the bitcoin p2p network supports transactions that are completely arbitrary data or spam. The concern comes from whether you think nodes relaying 100kb files, uploaded anonymously for free could be an attack vector for bad actors.