It bloats the UTXO set increasing the cost of validation, among other things
Discussion
This is nothing to do with Taproot or Segwit. You are very confused.
I have been a professional software engineer for 25 years and studying bitcoin specifically for 7. I can assure you I understand the details of the protocol quite well. If you do not understand how the witness section is abused to produce spam then you should study bitcoin more deeply. I am not your tutor.