I hate when a show starts out with a certain vibe or feel, but then drops it as the series goes on.
Case in point: Doctor Who.
(I'll try and explain this without being spoilery or confusing people who haven't watched the show with unfamiliar terms. Doctor Who is a show that's hard to explain, so I won't be able to give this all the rant I would like to.)
Seasons 1-4 were great, because you got to see a story arc that didn't just continue over one season, but all the seasons. Seeing as the show started in 2005, (Yes, I do know the original show started in 1963, and that this is a reboot.) the CGI was cheesy and obviously unrealistic, but somehow it was fitting for the show IMO. The Soundtrack by Murray Gold helped strengthen the emotion you felt throughout an episode, and the character interactions were good, and funny when they were supposed to be. (Although compared to the 1963 show, it seems like every companion had to be a love interest.)
An example of the continuing storyline in Seasons 1-4 is the character Rose. She dissapears in the second season, but it ends on an unfinished note, so you know her story isn't over. That sort of excitement of a character coming back really didn't appear in seasons 5+
Seasons 5 and following didn't feel like they carried over a good continuing storyline. (They did, but it wasn't really great in my opinion.) Ignoring the obvious political correctness that was done in places, and the many innuendos made in seasons 5-7, the show lost the same vibe with more modern CGI. Many of the locations didn't feel memorable or like they were supposed to feel. And what's more, the characters just didn't feel as fun to watch as the characters in seasons 1-4.
I get offtopic a lot, be warned. I also often mention a Minecraft clone called Minetest. The clone is nowhere near playable with it's default game in my opinion, but it's at least the start of a good open-source voxel rendering engine, and maybe one day it might be decently playable.
Dragging on a show when it should have ended like 3 seasons ago. I've seen plenty of shows that were awesome, but should've stopped after a few seasons because there wasn't anything else to dredge out of the story. Like, it's ok to admit you've run out of ideas and just wrap up the story.
Also, I really hate lazy explanations in TV shows more than movies. It's a tv show. You can devote some time explaining how such and such works, because you actually have more room to explain things than a movie.