Warehouse 13 has never been a great show but it's usually lightly done and quite entertaining. The first season aimed at little more than that - vaguely The X-Files minus the angst, incoherent backstory and, let's face it, some of the smarts. The second season added a fantastic plot twist that made me laugh and then they built on that with just a tad of quite effective moral ambiguity.
The third season is now streaming on Netflix and the first episodes of the fourth have aired but something is way off. It's like a key writer or even the show runner left so everybody remaining is falling back on the least imaginative TV writing possible. For one thing the eps are now mostly solve-the-riddle format, something that's always been there but usually more in the background. These riddles should be the MacGuffins that drive the story not the actual point of the story - watching characters figure out something that's completely arbitrary and that we have no way of figuring out ourselves is quite pointless.
Season 3's bad guy similarly shows little thought. In the earlier seasons the main baddie was driven by understandable motives - greed, anger, revenge. Plus they had some connection to Warehouse 13 that added texture to the story. In Season 3 he's doing all these bad things because he's evil. Seriously, that's it - an artifact turned him evil. This descends into bottom-of-the-barrel pulp/comics writing. Oddly the show's creators decided to toy with his identity, very obviously withholding it by keeping him just out of the frame during numerous scenes and building up to a big reveal. And then we learn that....TAH DAH it's somebody we've never seen before! This is notably clumsy and almost makes me wonder if in fact they decided to change this person's identity partway through the season - otherwise this makes almost no sense except as incompetence. (Well to be fair we have met this person before but it was as a child so there's no way anybody could have drawn that connection.)
Then we get to the issue of the cliffhanger. At the end of Season 3 they take the big step of, gasp, actually destroying the warehouse. Boom, flames, gone. This seems like a clever way to push the show in a new direction but alas the start of Season 4 pushes a "reset" button and undoes all that. Even worse, undoes it in another tedious, connect-the-opaque-dots story. Hey didn't we mention there's an artifact that resets the entire world to 24 hours earlier? For no particular reason? The creators do try to complicate this a bit by stating that the reset will unleash Something Bad but since so far that has remained under wraps there's really no dilemma.
Warehouse 13 has never really bothered to fill out its background so a lot of it doesn't make sense or hold together. But as long as that wasn't a focus it didn't much matter, sort of how The X-Files worked until they tried to piece together a "mythology" out of unconnected stories until even fans gave up on it. Warehouse 13 might be headed down that path - we'll have to see how this season plays out. As a sidenote it's interesting to see how the show tries to position itself as science fiction when it's inarguably fantasy. But considering how confused the creators seem to be then that's not particularly surprising.