On the topic of "writing for yourself" in general, I was reminded of this quote: "[A] hack writes hierarchically. He writes what he imagines will play well in the eyes of others. He does not ask himself, What do I myself want to write? What do I think is important? Instead he asks, What's hot, what can I make a deal for? ... It can pay off, being a hack. ... But even if you succeed, you lose, because you've sold out your Muse, and your Muse is you, the best part of yourself, where your finest and only true work comes from." - Steven Pressfield, The War of Art.
So yeah, it's balancing between what you want to write vs. what you think the readers want to read because too often those two do not align largely. So what to do? please the crowd or write what you want to write? The financial (or fame) incentive also adds to the scale. Many authors who are well-known, likely write (or draw) professionally, meaning, it's a job. They pay their bills that way. So it's no surprise they are dealing with a market, and there's no blaming people for providing products that the market wants. Harem, for example, is (for the sake of this argument) a crowd-pleaser and can attract a wider range of readers.
As for staying true to yourself and stuff, that's also valid. I myself lean heavier towards this part. Yes, I picked two fandoms that I think are popular for the topic of my book, but I am writing it in perhaps the least crowd-pleasing way there is. I ain't deliberately trying to turn away readers, just structuring the story and its settings in a way that'd allow me to write what I want to.
Writing for myself is comparatively much easier because I really am doing it just as a hobby; I write when I'm bored, and I don't expect my webnovel to put food on the table.
In the end, is it a mistake to not follow market trends and please the crowd when writing? Yes, if you are trying to profit and or build fame. But if you are just doing it for fun, then just write whatever. I have like 70 readers, and that's 69 more readers than I had anticipated when I started my book. Honestly, I'm thrilled.
And to other authors, especially those who write as a source of income, I can't say much because I am not in the same situation as them.
I, however, do imagine someone doing both in different works. That is, they'd first write for the market, please the crowd, being a hack, and after making it big and attracting fame and building a reader base, then they'd write for themselves and tell their readers: this is me, this is what I want to write.
Has anyone ever tried that? How it went?