I think you’re right.
In the article, they mentioned that words denigrating the holy or sacred were the most offensive while in more recent times the most offensive words became words referring bodily functions, sex, etc. But now as you suggest, the most taboo words in the English language are slurs denigrating entire groups like various ethnic groups, religious groups, women and the elderly.
Some words imply the person you're insulting is unsavory. Some words imply "I have power over you such that I can do anything I want and you can't stop me."
The degree to which this violence is allowed in a culture also conveys the power of the word in play.
There're many categories of violence, and semantic violence can evoke any and all of those.
Even when Alan Pardew (and I take great pleasure in being the first to mention his name in this forum) called opposing soccer manager Manuel Pellegrini "a fucking old cunt" it wasn't perceived as a slur on his elderlyness. It was the cunt bit that got him in trouble - and, even then, not that much.
I feel like it's becoming a word describing people that have passed their prime (~35+ yo).
Yes, I'm fully aware that the word initially described people that were born during the baby boomer years (~1950) and that the people that are currently 35yo are millennials.
80 years ago was 1944 - not exactly a boom year. Most are 60-65-70 and would not consider themselves elderly. It's a very loaded word.
You go directly from middle aged to elderly, there isn't a step in between. Being elderly can cover a very wide range of years.
That said, I've had friends that were elderly in their mid thirties.. State of mind and all that.
(Rationale being retirement planning advisors encourage people to make the most of those first ten years (65 to 75) to do bucket-list things while (usually) they still can)