I think it's well understood at this point that it's pretty much about giving people some shared language to talk about needs in a relationship. However, even with that, there's some contention— "words of affirmation" specifically seems to get a lot of heat.
Like, yes it's valuable to be aware of your partner and use those observations to uplift them, but it can also swing into some pretty unhealthy territory too ("when you raised that issue with me, I felt criticized, and then my words of affirmation need wasn't met any more; if you love me, you need to demonstrate that by not raising things with me") or even becoming a demand for unrealistic, toxic positivity ("I need you to be positive about/to me no matter what; I will be dependent on you for my emotional well-being, and if you're ever not positive to me, I'll become sullen and depressed and it will be your fault").
So yeah, love languages can be helpful as a starting point, but you still need guardrails in place (for example, a professional counselor) to make sure it doesn't get used in a manipulative, unhealthy, or unfair way.
If you say stuff like "people communicate and reciprocate love differently", then it's neither science nor pseudoscience.
If you say stuff like "these are the five specific love languages and everyone has two", that's either science or pseudoscience, and I'll give you two guesses how rigorously tested the hypothesis is.
Can't write a best-seller framed like the first one, though! People eat scientism up.
just like MBTI this is not an absolute where these types define your personality and predict your behavior that you can't escape. that of course is nonsense. but both are useful to get a better understanding about yourself, your partner and your relationship.
talking about these things with your partner works, and that helps to improve your relationship. i can confirm that from my personal experience.
