The article gave a range of explanations why Olive Garden has hit hard times, and I have no reason to believe that those problems are not paramount. But there might be another added reason that the article overlooked.
After the Affordable Care Act passed, the owner of the company, Darden Restaurants, was very critical publicly of Obamacare and said that they were going to cut back their full-time workforce and give employees fewer hours, making them officially "part time" so as to avoid hitting the guidelines that would require the company to pay for health care. Given the drop in patronage, it's certainly possible that such a public position bothered a lot of customers who are now, in turn, avoiding the restaurant. I don't say this on a whim, but from personal experience.
I have a friend with whom I get together for lunch once a week. Every once in a while, we've gone to Olive Garden -- we particularly liked their "Never-ending Pasta Bowl" promotion. Hey, sometimes a guy just has to go for quantity. But after the public statements, my friend sent me an email to say that Olive Garden was now off our list, that he wouldn't go there again.
To be clear, much as I hate the position of the owner, I'd have been okay going to Olive Garden occasionally when they did that pasta promotion -- though perhaps less often. But my friendship is stronger than my love of a pig-out pasta meal. So, if my friend refuses to go, I will support him. (And yes, I could go to Olive Garden on my own, but it's a long drive, and having company on the ride helps.)
Anyway, the point here is that if my friend crossed Olive Garden off the list, it's not unreasonable to think that others have done so, too. And though I'm not aware of other restaurants in the company's holdings doing poorly after the owner's statements (they may be, but I'm just not aware of it), if a place is in trouble to begin with, adding another reason to stay away is never a good thing nor helps much...