It was in the game for so long and I know so many og players (and new ones at that matter) that really like it, and I agree with them, it just looks way smoother and nicer imo.
Take League of Legends for example, there is new cursor in it but they still have option for "Legacy Cursor" for people that like using it.
Can you do same thing for Sea of Thieves please? Add option for Legacy Hitmarker, I bet that a lot of people would have it enabled. It can't hurt the game in any way, it can only make it better and more fun to players that like it more than new one, and it's fairly easy to implement. Rare, please consider.
Edit: as u can see in comments most of people agree that old hitmarker is better and those who dont agree also agree on fact there should be option to toggle between Old/New hitmarker
