Well first off it is entirely possible that there are people who have been introduced to the concept of love languages in a way where they never questioned them critically, and merely pointing out that I think they are "bunk" might start someone down that path of questioning.
On top of that, however, I specifically compared love languages to other things which people might have already examined critically. Since this is HN, probably the most cogent item from my list is zodiac/horoscope, as techies tend to be fairly dismissive of it already, and therefore might have the realization (after reading my comment): "oh wow, I've been believing in love languages this whole time but been dismissive of zodiac, even though both have the same amount of evidentiary backing (~ 0)". However, I actually think "learning styles" is a better example because it is something a lot of people believe in (something like 90% from the surveys I've seen), even though in reality there is almost zero experimental evidence for them as well, despite many biased attempts to do so. My opinion is that love languages are very similar – people believe strongly that there are certain actions/behaviors that they are most receptive to when it comes to romance, but that fundamentally people just want to be loved in a much more generic way and that if the particular way in which love is expressed matters that much to you, you are probably focused on the wrong thing (missing the forest for the trees).
To really spell out why this is bad, let's look back at learning styles: someone believes in learning styles, which don't exist[1]. Specifically, they believe they are a "visual learner". As soon as this belief forms, it almost instantly becomes a self-fulfilling prophecy – they think they are a visual learner, so whenever they are faced with learning something in a non-visual way they don't try as hard, and therefore do not learn the material as well. They are effectively self-sabotaging by having this constrained picture of themselves in their head. There is no reason to believe that people who take love languages seriously will not suffer a similar fate. Imagine someone who thinks of themself as a lover whose primary love language is "physical touch", so when someone demonstrates love in a way that is not touch, they say to themselves (maybe not in an explicitly conscious way): "hmm, this isn't as compelling as it could be because I'm a physical touch lover – I wish my partner demonstrated their love with more touch".
In essence, I feel that all of these things, love languages included, are artificial and mostly arbitrary labels (some more arbitrary than others) which only serve to constrain your breadth of experience and openness to new things, resulting in unfortunate self-fulfilling downsides with no clear upside.
[1] https://www.apa.org/pubs/journals/features/edu-a0037478.pdf