I don't really see her as an explorer as so much as someone that wants to learn about themselves and tap the mystery of who she is. She has also been shown to have an undying need to help the ones she loves. When on Ocampa, this translated to her wanting to leave the planet, to see what her people were capable of outside of their hamster cage. On Voyager, it translated to exploring the unknown and also exploring her mind and powers while still caring for the crew as a nurse. When I look at it that way, her unlocking her powers and looking into herself, and having a need to go back to where she came from to help the people she left behind is very much in line with her personality and is a reasonable ending to her story arc.
For me, labeling her as 'an explorer' seems too simplistic. Now this isn't to say that I'm completely happy with her being written out of the books, it would definitely have been nice to have her around once in a while just being Kes and exploring her as a character, but the series itself, elevating her to super-being seemed to make that pretty difficult.