Not necessarily my experience. I wrote (and I am writing) several academic documents with it. There are its quirks, of course, but with good classes such as memoir, I don't feel the need to do a lot more than basic customization in the preamble. Still is a good tool for me.
For me the memoir class made LaTeX worse. The titlesec package is more customizable, easier to use, and reduced the size of the preamble significantly.
That's if you need to customize headings. I usually can keep using the standard ones, so that's not my case, and I suspect this also applies to a lot of people.
