I do not warn about airplanes when one of them crashed but when 60% of them crashed if the flight was longer than one hour, I'll take the ship.
I don't warn not to take the String class because I have a bad feeling but because I analyzed the code and brought that into the context of an MCU without a memory management unit like modern PCs have and with only very few kBs of RAM. Do the same and you'll get to the same conclusion.
In this thread the OP hasn't told us he has a specific problem. Nevertheless, in my opinion, I'm allowed to point him to potential problems that may arise from using the wrong libraries.
And I am a programmer, I also use the C++ string class in my programs for the PC but that's no reason to do the same in a completely different environment.