I agree, I've seen quite a few people complain about the companions. I think some people have a certain expectation of what they think their companions should be and how they should behave. I see a lot of resentment towards Shadowheart, saying how mean she is but once you get to know her, you realize why she is like that.

Another thing that is important when playing a video game that has companions and dialogue options is getting to know your companions through dialogue.

Larian did say that once the full game releases they will include an approval rating and also a romance indicator to show how much that companion may like or dislike you.

To use Shadowheart as an example again, the first time I played, I missed finding her on the ship and when I met her on the beach she was really mean.
The second time I played, I found her on the ship and tried to help her, when I found her on the beach, she was a lot nicer.

Also, I think your companions react to you based on what race you are. I notice with my human female both Shadowheart and Astarion were neutral but when I made a female elf, they seem more comfortable around me, especially Shadowheart. She was even nicer. I found that to be interesting.

At the end people liking or not liking their companions comes to their taste and we are all different.