There's a world of canon references in "The Dying Detective" alone. A world of betrayal, actually, and quite a bit of angst and Reichenbach parallels worth mining. That's without going into the aftereffects of TST and all it was trying to do with The Sign of the Four> Instead we get this really cheap soap opera. High production value, brilliantly executed, great acting with what they've been given (both Martin and Amanda were simply brilliant), but at bottom it's built on a skeleton of candy floss.
I don't know. I'm obviously upset and more than a bit worn out, and maybe that's driving this. I really don't know. I just know the whole thing felt horribly cliched (... again ...) and like they had to keep upping the stakes because the center just wasn't there.
ETA: Though I will say, I'm really enjoying the faith = suicide thing they've got going on, along with Sherlock quoting his frustrations with Watson's "romanticism" as theater. Stepping away from cold reason / intuitions + romanticism / death of self and the Kierkegaardian leap of faith...
Look, I'm not a phil religion scholar for nothing, peoples, and this is honestly more fodder than I ever expected to find in this particular universe.