I know you have good intentions with your advice, and maybe it has come easy for you
But for a lot of people, developing social skills and "a nice personality" has been a life-long struggle
There is a big overlap in STEM with the autism spectrum, with ADHD, with anxiety and trauma, all of which make it very hard for people to "fit in" and develop social skills that come easily to neurotypical people
So while I share your sentiment that soft skills are valuable and are worth developing. Please don't judge others for not doing so, and keep in mind that they might not even have the capacity to do it, even if they want to. They might also have had a really hard time their whole lives being judged and rejected by "normal people". Please have some extra empathy with them
Here is a "goofus and gallant" anecdote drawn from real experience.
Goofus and Gallant are both on the autism spectrum, and tend to be blunt in ways that come off as rude. They are both very stubborn about what they consider high quality code, and guard their status as domain experts in particular technologies.
Goofus gets incredibly defensive when they don't understand something. Goofus talks over people in meetings. Goofus is generally rude and hard to work with.
Gallant wants people to understand what they understand. While blunt, Gallant is also patient in walking more junior engineers through their thinking. Gallant isn't quick to give praise, but gives it when earned. Gallant doesn't want to be the only person who understands how something works.
These are based on several real people I've worked with, and the Gallants are some of my favorite coworkers. Bluntness might put some people off, but it doesn't bother me as long as the purpose of that bluntness is to connect with people.
I'm sure it's more complicated than that, and everybody has a different brain, and maybe it's much harder for the Goofus for reasons I can't see. But I have encountered enough Gallants that I know it is possible for neurodiverse people to still be themselves AND kind and empathetic. I certainly hope it's true of myself, not that I always succeed.
But for a lot of people, developing social skills and "a nice personality" has been a life-long struggle
There is a big overlap in STEM with the autism spectrum, with ADHD, with anxiety and trauma, all of which make it very hard for people to "fit in" and develop social skills that come easily to neurotypical people
So while I share your sentiment that soft skills are valuable and are worth developing. Please don't judge others for not doing so, and keep in mind that they might not even have the capacity to do it, even if they want to. They might also have had a really hard time their whole lives being judged and rejected by "normal people". Please have some extra empathy with them