Is color theory subjective?

You have bad taste in colors. Complementary colors look terrible together

Color theory is subjective in the way that certain color combinations can mean different things.

there are colors that are naturally complimentary and will look good together, but they will convey different information in different contexts.

Take purple for example.

Gold and purple are complimentary, and can be short hands for wealth or royalty.

Green and purple are not complimentary, but can be a short hand for something poisonous.

it's all in how you use color theory to convey your intended idea.

The physical facts about colour are scientific, thus 'fact'.  How humans have interpreted colours in various societies and at various times in  history has varied hugely. Thus 'subjective 'just about covers it!

You gave produced a good list of colours which go well together, but many would disagree with you.

I recommend reading "The Secret Lives of Colour" by Kasia St Clair.  Read at least the introductory chapter, even if you don't read the short chapters about individual colours.

The go to guy for colour theory is Joseph Itten.  I suppose the more you learn about it, the less subjective it is.

The theory works, but it is not proscriptive.

The more you know about color the less it seems like rules and the more it seems like guidelines. Which of the 45,000 hues of purple are you referring to?

My favourite colour combination is red and black. Combined with the screams of the souls in hell.