The 14th amendment was written to give former slaves citizenship. It was used correctly to give citizenship to anyone born in this country, regardless of whether their parents were citizens or slaves or whatever.
I'm not saying a pregnant woman from another country should be able to fly to the US in 2018 and have a kid who gets automatic citizenship, but that is the way the constitution is worded... and as mentioned before, there is over 100 years of precedent to overturn if you want to change the way the law is interpreted