The word "sophisticated" has several meanings. As you have already stated in your question the meaning in context being "a person or their thoughts, reactions, and understanding, being aware of and able to interpret complex issues", I will try to elaborate on this meaning first before going into the details.
Being sophisticated does not mean being, 精明 (smart) or 老练 (an old hand). Being sophisticated is usually related to EQ rather than IQ. A sophisticated person is usually someone who is able to handle complex situations in a social setting rather than someone who can solve a complex algorithm. From this, we can infer that this person must be mature in his/her thinking. Maturity comes with experience. Sophistication does not require the over-experience of an old hand nor the exposure to worldly affairs.
With that, the following examples is what I feel appropriate by inference:
- 熟女 - a sophisticated lady
- 成熟的观众 - a sophisticated audience
- 经验丰富的人 - a sophisticated person
Another meaning of sophisticated would be refined:
- 品味高尚 - having a sophisticated taste
Both meanings can be applied on the same person and they usually do when applied to a person.
Based on your updated example, the meanings above would not apply. In this case, sophisticated takes on the meaning of "advanced" or "ahead of times". I would translate it as follows:
虽然入世未深,但他的想法比世界上最好的哲学家还要超前...