I took a seven year break on this series half way through the third season because I thought the writing had become sloppy and poor. I resumed watching partly because a friend had assured me the fourth and fifth season were better, and partly because I had time on my hands at home because of COVID-19. Getting through that season was a bit of a chore, but the fourth season is an improvement. At least from my point of view: they concentrate mostly on the episodic mysteries. There were of course predictable elements: Sherlock is cleared of the (almost justified) assault he committed at the end of season 3 in a deus ex machina move that also introduces a character who remains their foil for the season - Sherlock's father (John Noble). And, in typical style, his manoeuvrings feel a bit like they're nailed on to the plot structure. And - again typical - come to a head in the final two or three episodes of the season. Although oddly, they wrap things up fairly cleanly without leaving us with a cliffhanger as they usually do.
I loved that they worked in "Rache," "German for revenge," which is a significant point in the first episode the British "Sherlock." Better yet, they manage to twist it into a very different clue. It was a hell of a nod to their counterpart series - and one that still worked fine if you'd never heard of "Sherlock." Quite elegant.