- really, very
- just
- totally, completely, absolutely
- thing
- some
- rather, quite, somewhat, somehow
- ...
Like all style advice, it's not really a "rule" to follow, but it's surprisingly difficult to avoid some of these words. I struggle with "really" and "just." It makes you work, but your language is better for it.
I think many swear words fall into this category of words that are really easy to use. These lists always heavily feature strengthening modifiers, and swear words are often strengthening modifiers. Especially "fucking" which is just a really fucking versatile thing to use.
I wouldn't say relying on these crutch words is a lack of knowledge or fluency, but maybe it's a lack of versatility and easy varied expressiveness. Relying on these crutch words makes it harder to be specific.