I recall really enjoying the first season when it was new and the second being pretty good but not quite the first. The third I don't recall as being particularly horrible but it was downhill enough to where I had lost interest in making an effort to keep up with the series.
Just now I decided to check season 4 and in the first episode they have a cop call simple video editing brilliant then have a time-lapse where they literally scroll through several seemingly interesting cases taken from Sherlock Holmes books that could have been rewritten into interesting episodes. Instead they skip those and proceed to have a case with the following stupidity. A kid records fake skype video in the mountains, sends it to his dad on his dad's birthday to trick him that he can't make the party, hides himself in his car in a fake vinyl car seat bag(?) then has sudden death episode (aneurysm or something) before revealing the surprise, sits in the car dead for a week and then a drunk driver crashes into it and it explodes into flames and Sherlock figures it out because there were 2 types of vinyl in the burned mess. That is the stupidest fucking plot I have ever heard in my life.
Even if it's just a piece of an episode that is horse shit. There's no way the same writers are writing this fucking garbage as season 1. Oh and then it goes into a story about flash drives that could have been copied easier than floppy disks for a decade but mysteriously weren't and some otherwise crap story pulling threads from openings left in past seasons.