I don't agree. It really depends on your genres, the story, the characters, and the audience. For adult fiction, I think the appropriate expletives add to the verisimilitude of the story when appropriate. A gangster is not going to say, "Gosh darn it, I shot my damn foot." I don't see how swearing "generally" makes the writing weaker. I think weak writing makes everything weak, including excessive or wrong use of expletives.
While I understand where you're coming from, I think swearing often weakens a story for some combination of the following reasons: (a) it draws attention to the swearing and away from the story, (b) not swearing in a situation where it's one possible likely act makes the author think more thoroughly about one's options for the scene, which means that a better overall picture can be put together and that if a swear word is used, it's used because
it's the best tool for the job, and (c) swearing, especially if done gratuitously, can make the story less accessible to a number of readers.
I'm definitely not advocating the "Gosh darn it!" approach, though.

That's generally only useful mockingly or perhaps in the occasional looking-at-authority-figures-to-see-if-it-gets-one-in-trouble sort of scene.
When you're "restricting" yourself to a weaker curse word, you're not being truthful to the character and you're censoring as an author, based on your own issues with cursing. To me, that's truly a "restriction" you put on your work, and it can't be "more powerful." Now if you're saying you only use curse words to bring power to your story -- that is understandable, but only when you're not using it so sparingly that it jars the readers.
A writer should always strive to use the right word, the most appropriate word. And that include swear words.
As authors, we decide how to expose our characters to the reader, even though our characters may choose how to act. We can take one act of a character and change it to another and have the second be no less authentic, or perhaps be more authentic, than the first. There's more than one exact story that's true to a given character and more than one exact verbiage that's possible for a given character, otherwise editing would be little more than checking for comma placement.
The reason for a restriction to relatively light swear words, where one chooses to do that, is that that restriction makes the writing stronger--the light words can jar enough to be felt and evoke a significant response from the reader, but not so much that it draws them into a meta-awareness mode about the writing style. Interestingly, come to think of it, they can even be effective in a story that's littered with harsher obscenities, since their very rarity in such a story could lend their connotations weight.
I'm not saying swearing should never be done, but that a writer's default should always be not to swear unless there's a strong reason for it. Like breaking the rules of standard written English: there are times when it makes sense, but it's something to be conservative about.
Of course, we all have different ideas about exactly how to write, otherwise we'd have nothing to say to one another.
Best,
~Terry Lee Wright