I definitely see your point! Of course, your argumentation was a reply to someone who claimed that "Olicity tanked the ratings". As you might be aware, the Olicity shippers are using exactly the same arguments to show how important the Oliver/Felicity love story is for the ratings (and by implication, for the show itself). One very persistent trope in the Olicity fandom is that the ratings drop in season four (more specifically after 4X16) was due to the Oliver/Felicity break up. Apparently hundreds of thousands of viewers were so heartbroken that Oliver and Felicity were no longer a romantic couple that they just stopped watching. This is an idea that is very entrenched in parts of the Olicity fandom (I've personally seen this arguments dozens of times on various forums and fan spaces). So, according to many Oliciters Laurel's death didn't have much impact at all on the ratings, as opposed to the lack of Olicity romance.....which kind of implies that the audience at large are Olicity shippers!

In fact, the Olicity fandom has used the ratings' argument to "prove" that Felicity/Olicity/OTA are the key to the show's success since season two. I remember seeing charts on tumblr, where Oliciter bloggers would connect any dip in the ratings with a Laurel-heavy episode, and every increase in viewers/ratings with the prevalence of their girl/ship/OTA. Of course, the fluctuations in ratings probably have very little to do with Olicity feels (or the prominence of their much-disliked Laurel), but this hasn't stopped many members of the Olicity fandom from believing that a secondary hacker character and her love life are the show's big draw....just check any oliciter-dominated forum, and you'll see how they still cling to the idea that casual viewers have the same preferences as themselves.

So, when someone claims the opposite, i.e blame Olicity for the decline in ratings, my first impression is that they're just taking a page from the fandom that has invested the most in propping their girl/ship/fave constellation during "Arrow's" five years of existence. Because TBH I don't think that any Laurel fan/general fan (at least not until LL/BC was killed off) would be entitled enough to believe that the show's mainstream success was due to ONE element, which is not even very popular anymore.