I never was a guy who had "idols" in the sense OP said (including clothes, lifestyle etc.). Everything only belonged to the playing style or in other words: To the player on the court (or on the football field, the track and so on; I was interested in many sports, though tennis was always on top). In my inner circle of friends at home (apart from school) nobody cared much about clothes or any superficialities.
But I knew some other guys who were exactly different: They had the clothes of the stars but always had to ask me how they played in their last match.
And I made another observation: If we played team competitions against other clubs, my teammates with the "right" clothes were always overrated before the beginning compared to me when I just came along with a “boring” shirt, the racquet under my arms and often already wearing my tennis shoes.
As for when I was a bigger fan, back then or now, I have to say: Rather now! In my youth so many other things were interesting, and my friends and me thought the world belonged to us. We were busy with outdoor activities almost all day, and everywhere was something new to discover. There was no place for really big idols, we were our own kings (or wanted to be). If I had the time I watched quite a lot of sports though, much more than movies.
But then when I got older, everything became more monotonous. The other people changed more than I did. Increasingly they lacked enthusiasm for anything special. Always the same parties, always the same conversations about everyday life (school, job, relationships etc.). And the worst: Contrary to the old days appearance now is more important than intrinsic values. Deep inside I’m bored by this, so being a fan is one method to preserve my own enthusiasm and to flee from everyday life for a few hours.
Another reason why I watch more tennis compared to 15 years ago is of course the internet. Back then I had to rely on regular TV programs. Now I watch almost every Federer match regardless where I am and also many old matches from Youtube or other sites.
And as a fun fact: Now that I’m over 30 I own my first Roger Federer shirt. It was a surprising birthday present from my mother.