I didn't get into a lot of advanced stuff - just defined a few "newcolumntype"/"newcommand" and used them everywhere but that freed me from formatting worries and let me focus on the content.
For me the worst is tikz. I know it’s not exactly latex. But I wished it was easier to use. The output is so good, but it’s so damn hard to learn.
But yes, I know what you mean. I use the cargo cult method for writing TikZ code myself. Look for examples of people doing something similar, then poke at the code until it does what I want. I am slowly developing some glimmer of understanding, though. I figure in another 100 years' time, I'll be a TikZ wizard at this rate.
https://github.com/fhackenberger/ktikz
However, it is not quite as helpful as latexdraw was for pstricks.
That said, I am not sure how much of that difficulty is due to tools lacking and how much is due to "describe vector graphics as code" being a hard problem.
More in detail (I refer to [1] for a complete discussion):
1) It makes structured editing possible (and that is its main mode of operation). So if you want to mark your text with "semantic" markup you can do that, and in fact that is what using the software leads you to do.
2) It is controllable via programs
3) It has advanced typography (including mathematical formulae at the necessary level for professional mathematicians, as far as I can see), and it is pleasant and easy to work with: you can concentrate on writing, letting the program take care of the visual appearance and you do not need to interpret the sources while you are editing, to figure out where is the text that you want to edit
4) It has user-definable keyboard shortcuts that further help entering structured text
... and I feel it is enough for a short list of the features.
Back to Scheme. The development team is debating on which Scheme to use for the future of TeXmacs, and the debate is taking time. Here are some experiments [2],[3]. The current software (with Guile 1.8) works smoothly, with full functionality. For Linux installation, I chose the static binary they provide ... because on Ubuntu I don't have Guile 1.8 ;-)
[1] http://cahiers.gutenberg.eu.org/cg-bin/article/CG_2001___39-...
I hope that will help to bring the development forward.