It is complex/complicated enough to be difficult which is both good and bad; good in the sense that it is extremely powerful and features we might not need now we can surely use later, and bad because there are a lot of variables that come with those options. One thing that adds to the complexity is that everyone seems to approach animation from a different perspective (especially digital versus traditional) and OpenToonz is striving to meet the needs of both.
For those on the edge... not sure if OpenToonz is what they need... I recommend using the OTX release (by Turtletooth).
I put it on a USB stick so I can take it anywhere with me (although note... as of a few updates ago the main OpenToonz release can easily be made portable too).
As for working through the complexity... I recommend starting a small (test) project and each time you run into an issue post a question related to that issue here in the forum.
Someone will jump in and assist. Heck, don't wait for an issue to pop up... find a place to post your progress and invite others to give you feedback.
It's like that old saying, "How do you eat an elephant?"
Answer: "That's not important, we're too busy animating one frame at a time here." ;)