Everything about the first three seasons are fantastic, even the theme music is addictive.
The personalities, the puzzles, the way the people interact with each other. The cast is perfect and Benedict Cumberbatch is mesmerizing.
Then they blew it. No one wants to see their heroes incapacitated and out of their minds repeatedly. Hated the Eurus thing. And I'm sick of Moriarty. As he would say, boring.
Please make a season 5 which let's the actors solve and snipe at each other. And develop the other characters. This could potentially be one of the best things ever on TV.