I still think that a brilliant math professor who's secretly a ruthless mob boss would have been far more interesting than yet another chaotic evil madman who doesn't care about anything but watching the world burn or whatever. Obviously, they'd need to flesh him out as a more distinctive character first, but it could be done. Disney did it:
Literally the best version of Moriarty to date. Prove me wrong.
A minor quibble, admittedly, but I don't like the gay jokes the show keeps making about Sherlock and John. Not so much because I find them to be unfunny and immature - although I do - but because they're not justified by the context. What I mean by this is that for all its faults, one thing the show handles very well is its portrayal of Sherlock and John, and their relationship. They have a great friendship; unique, certainly, but also funny, touching, and believable. They're not just bros who hang out and do stuff together, they have a real connection. And at the same time, they're both clearly straight men. There's no real gay subtext or homo tension, at least not compared to something like, I don't know, Frodo and Sam from LotR. So anytime someone makes a joke about how they must be gay, it feels like it just comes out of left field. They're gay? They're gay because they work together? They're gay because they happen to share an apartment so they can split the rent? They're gay because they dare to be close friends who trust and confide in each other?
It's unnecessary self-deprecation, in other words. It's like the show feels the need to occasionally turn to the viewers and say, "No homo, we promise!" as if we're suddenly going to forget that they're just friends. Because they're talking to each other about their feelings and stuff, and we all know that only women and gay men do that, right?