The type of material that authors write depends on what drives the author. To your point, many would write about what is trending in the market and not what matters to them. That tells me that money matters to them and I would not think ill of that if that is what fits their situation. I am not a writer but indeed, writing (or doing) about what matters to you or what you love is certainly an inspiring one.
I have read different reactions about existing and dominating market platforms like Amazon. Some say it is good to tap into their system because it already built its strong brand. It attracts many people so thus the great exposure of your product if you're on board. Others have the same perspective as yours so they opted to run their own web page and grow it organically. I do not have much experience on the two options but they say the organic website will help you grow your brand. So I guess if you're up to that then maybe you can give it a try.