Before the Goddess of Magic Mystra became a goddess, she was also a person of great talent.
Otherwise, she wouldn't have invented numerous powerful spells and become a goddess.
It was an unprecedented accomplishment; she was the first mortal to ascend to godhood.
It was also because it was unprecedented that there was nothing to learn from.
Before truly becoming a goddess, Mystra also did a lot of probing into security and freedom restrictions. She found that becoming a goddess wouldn't have any security dangers and gladly became a goddess.
However, she never expected that becoming a goddess would completely erase the innovative ability that she was so proud of, though it indeed wasn't life-threatening in any way.
The power of the natural laws sealed off the insights and creativity that she had accumulated from her mortal days.