To wit, if we read it as "subject to the laws of the land", then the invading army exception does not make sense, invading soldiers are subject to the laws of the United States and have been tried and convinced of violating them. Note, diplomat exception still makes sense, they _are not_ subject to the laws of the land.
So, how do you define jurisdiction in this amendment in a way that covers both invading soldiers and diplomats? I don't think it is super straightforward.
To put good faith on the table, I ultimately agree with your opinion here that birthright citizenship is settled and the vast majority of folks arguing against it are doing so in bad faith. But I also recognize the text of the amendment has holes to my eyes and could be updated for clarity.