Tikz is misplaced in this list; it is how you make any kind of vector drawings in LaTeX. It's not the only way, but perhaps the best documented and most expressive one. If you have any such drawings in your work, you won't get around putting some effort into it. Not comparable with boxed theorems or fancy headings.
Tikz is sometimes useful, but it can also be a massive time sucking pain in the butt.
I mean it is one of the few packages that can actually manage to annoy LaTeX fans, which is really saying something.
I think the annoyance with TikZ is twofold: (1) it tries to do a really hard thing (create a picture with text in a human writable way), (2) it is used infrequently enough that it’s hard to learn through occasional use.
That said, nobody makes you use TikZ, fire up Inkscape and do it wysiwyg.