Because there’s no built in fan base with original work. They wanted quick easy money.

But this begs the question: why didn’t they just write an original series instead of seemingly doing everything “wrong”?

You answered your own question, friend:

Sounds like Netflix writers are a little too eager to make this work their own.

They basically character assassinated and/or completely changed everyone, including the female characters they were trying to prop up as being strong (Yennefer in the Netflix show is a screaming whining mess who can’t do anything on her own and dicks over Ciri while Yennefer in the books and games takes shit from nobody, especially when it comes to Ciri and Geralt). They even (surprised I am even saying this) blackwash Fringilla in the Netflix show, whose entire point in the books is that she looks and is extremely similar to Yennefer during a time when Geralt and Yennefer were broken up. Them expanding on Istredd (except for the weird pedophilia with a young Yennefer) and the head teacher of Hogwarts Aretuza was pretty cool, but the writers literally shoehorned their own issues and takes on the show with no respect to the original material.

Fwiw, they also bullied the hell out of Cavill on set for trying to keep things faithful to the books and playing the games because A) he’s a Witcher fan and 2) it was helping him get into character.

It’s clear the public wants a faithful portrayal, but that’s the one thing the writers just aren’t willing to do for some reason. I can’t help but wonder why

Because Netflix doesn’t pay for the writers to solve problems. Have something that doesn’t translate well to screen? Don’t try to figure out to how to make it work—get rid of it. Have a character arc or plot point that moves “too slow” for modern audiences? Good news, that’s an action scene now, and there’s a gun, or a sword… or a gun-sword!

Sure, the writers can be blamed sometimes (especially when they are also the show runner… cough Davis S. Goyer cough), but a lot of the time, it’s studio pressure to make something quickly and that follows a formula that some exec believes is the golden ratio of shit to slick.

But this begs the question: why didn’t they just write an original series instead of seemingly doing everything “wrong”?

These people don’t care about the material, medium or the consumers - they care about the money. Nothing else. So if someone has an unique and brand new idea for some fantasy series that doesn’t have an already established fanbase, it is a gamble to actually produce it … will it flourish or flop? You simply don’t know beforehand, because the public hasn’t reacted to the idea yet.

Buying the rights to an already existing franchise with an already existing fanbase and then producing a series about it, that’s a lot more likely to make money - plus free advertisement as the already existing fanbase will make sure to share and discuss the upcoming series, internet tabloids will churn out articles about rumors and leaks and the like, and especially when you then do something outrageous like deliberately butchering the story and/or characters or shoehorning your own shitty ideas into the series, you will get even more media coverage for free: angry fans sharing their opinions online, people watching episodes because they couldn’t just believe how bad everyone else said they were (or watching them so they could join internet discussions about how bad it was), memes, blogs, discussions … you get the gist.

To those people, there is nothing “wrong” with that. On the contrary - it makes money, so it must be right. Fuck the source material. Fuck the author. Fuck the fanbase. Their opinions don’t matter als long as they stay agitated and keep consuming what we dish out - that’s their mindset, and producing deliberately shitty shows even helps with that, as paradoxical as it may sound at first.