Would be better if Notion did it, but if you're on Android using Firefox, then install uBlockOrigin and add the following filters:

  www.notion.so##.checkboxSquare:upward(2):style(width:30px !important; height:30px !important;)
  www.notion.so##.check:upward(2):style(width:30px !important; height:30px !important;)