I think it is worth watching, but that you should just be prepared that it isn't going to be the same as TLA.
For one, the setting is quite different as it's set about seventy years after TLA and the world is progressing to about 1920s-1940s technology. They also don't travel around as much as in Aang and co did in TLA, instead Korra usually stays around the same local area (Republic City) most of the time, so LOK doesn't exactly have that same epic adventure feel that TLA does.
I also get the impression that the creators never knew if each season would be the last. I think they were told they were only going to get one 14 episode season at first, so they wrote book 1 of LOK as a self contained story, then that got extended to two seasons so book 2 was also a self contained story etc. So the seasons don't really build off of one another in an overarching arc the way TLA did.
Also, each season/book (14 episodes) is shorter than the TLA books (22 episodes), so they don't have as much room for character development episodes or lighter, fun, filler episodes. This can make LOK seem like a very action-packed ride that piles on problem after problem after problem until the resolution at the end of each book.
I think the creators did well with what they were given to work with. As others have mentioned they had some limitations due to executive meddling and there were some poor choices made initially (with the focus on the silly love triangle drama) but the series did pick up and even the 'worst' season (book 2) had some really good episodes (Avatar Wan's story). I think book 3 and 4 have been especially good and probably just as good as TLA in terms of quality.
The animation and art style is definitely an improvement from TLA, LOK has some beautiful artwork and the characters are much more realistically drawn.
I think LOK definitely has its strengths as well as its weaknesses as a show. Though there are many callbacks to TLA, it's different from TLA for a number of reasons. Many fans of TLA like TLA better, but that doesn't necessarily mean LOK is bad.