I do believe that with any human, interests come and go. It's part of developing and growing. The brain is extremely dynamic after all and highly unpredictable.
And I agree that there are many "categories" within the furdom as well, as it is with anything else related to hobbies, interests and/or life views for that matter.
Personally I've always had an interest in animals. How their brain works, their social structure, how they evolve... But also how they act, feel and see the world around them. Sometimes I even feel the human species lacks things that other animals still have. Miss them even. Like how manoeuvrable ears become a vital part of body language.
It's an interest, a fascination if you will. Maybe even a fantasy sometimes. But bottom line, I still feel like I am fully of the human species.
When I entered the furdom I had known about them for a long time without paying them much attention (though never thought badly of them), though I didn't feel like I knew enough and began to read about the whole thing and came to the conclusion that I "fit in". I haven't become more of a furry or changed. Rather just evolved and gained more insight and knowledge.