Hall of Fame
I have more than 1 favorite player for different reasons. I used to hate Djokovic, like say 09 when he retired against Roddick and was overall just kind soft. I probably have old posts in this forum from around then basically trashing Djokovic.Your argument essentially boils down to: "If you don't like my favorite player, you aren't a real fan of tennis". Maybe some people just don't like Djokovic because they don't find his game very fun to watch. Is that so bad?
He's won me over.
I love Nadal for certain reasons, and I think 12 French Opens is by far the greatest accomplishment ever in tennis, and nothing is really close.
I like Sampras and Agassi, because I grew up watching them. I like Federer, because he's basically the last great player we will see of that mold.
It's not just, "if you don't like my favorite player, then X,Y or Z"
Novak's game is ridiculous, if you understand what he's doing. He's not just counterpunching and getting balls back, he's slowly picking you apart. He's like Floyd Mayweather, but way more offensive. Some people don't just don't understand what he is doing to win, or as you said his game is "not very fun to watch" those are fans of 1 player, not necessarily fans of tennis, as a game. If you like tennis as a game, his game is pretty textbook and difficult to not like, his game is almost like Agassi and Federer combined.