I dont understand why people are against an in game parse.

Common reason I see is to prevent toxicity. News flash it already exists so it why would making an official parse increase that when likely everyone already using one would be the same people to use the official one
Another common reason I see is to prevent harassment. News flash its the internet, use the saving grace called reporting and move on with a blacklist. Reporting people for using parses as harassment wouldn't change, neither would it being a reportable offense change.

Literally nothing would change beyond giving PS4 players access to a tool that arguably many want.

Why is everyone so afraid of information. You're going to find negative people everywhere in life and an MMO is no different. If you think anywhere on the internet is a safe haven, please share your ignorance with me. There are really no tools/incentives for self improvement in playing besides a bad one called hall of the novice which doesn't help people play their jobs better. Something where even a curious player could view and compare, or ignore and continue playing how they want would be a great addition and might even help people feel incentivized to try and play better.