This is what I always try to emphasize to the junior guys I've worked with. I read the book Flowers for Algernon when I was younger and it was the thing that stood out to me the most.
It does not matter how right you are if no one likes or will listen to you. Unfortunately, being likeable is inifinitely more important than being right. Your job is to strike a balance between both otherwise stupid likeable people will be dictating the direction.
Being right about most things more often than everyone else is an inherently likeable quality.
It's not really about being "likeable", but being persuasive. Don't put the cart before the horse.
You're correct that being right isn't enough, but if you make being likeable a direct goal you will come off as insincere and fail.