I just think the simplest thing is don't pursue an adaptation of something if you don't intend to heavily draw from the source material. If the show wanted to do that they did, they could have easily just developed their own IP; it's not like Netflix is any stranger to some C-/D+ grade fantasy/sci fi that make SciFi channel originals look like pure kino.
It's as if I wanted to make a Italian sub, but changed out everything on the inside to the point where the garnish and bread are the only things reminiscent of the original recipe. They're the same only in that they are sandwiches. And I'm sure the guest who requested the Italian sub will be dissatisfied with the tuna sub, because that's absolutely not what they were expecting.
Now say I make that sandwich as requested, but instead decide to put hot peppers and a homemade dressing. Sure, I'm taking a risk that I think either A) reasonably subverts expectations for the better or B) constructively improves upon a familiar foundation. At the end of the day, it's still an Italian sub though, we're still in the ballpark of expectations here.
I will always echo that if Netflix wanted to use the Witcher as a brand name, but still do their own thing, this entire show should have launched with a season of just Geralt being...wait for it...a ******* witcher. See given that the books and games heavily draw influence from folklore, Netflix had endless resources to craft unique, monster of the week adventures that built upon the fairy tales their audience heard as children. None of this needs to contest with established lore either. Geralt hunts monsters, monsters come from folklore, audience gets cool action with twisted tales on familiar stores and plenty of deep fantasy - seems to fit the bill. I remember Netflix had some documentary where they talked about researching monsters from European stories and all the concepting they did for it, but where did that actually come to pass? Across three seasons we get about as many monsters than you can count on one hand. But, some of the best content was when we actually get to deal with a world where monsters are real, and an ethical/moral/internal debate is tied up in it. The first episode of Season 2 comes to mind as what if like to have seen this show have more of.
Having Geralt hunting monsters for coin, occasionally showing a side of compassion, stinking his nose in the world, doing the things that make him special as a character seems logical. Crazy idea, right? Plus, think about it, a monster of the week series that dips in and out of the Continent would give them a free canvas to introduce audiences to the universe and express much of the world building the show lacked.
Plus, if an audience unfamiliar to any source material gets to see Geralt shed a life of murder-for-hire and solitude and gain a family, suddenly that character arc has meaning. We give gravitas to Geralt's connection to Ciri and Yen when they finally appear, and how it changes him has a character. The work to set up this evolution makes the pay off of what the show rushed to achieve fair more impactful.
I just hope that Netflix drops the license sooner than later and someone with more finesse at crafting media gets a hold of it. Showtime weirdly comes to mind, but really any of the high end folks would probably do better with it. And bring CDPR onboard, pay them, and lift their aesthetic. Much like Peter Jackson sort of creating THE image for live action LOTR, I think CDPR basically did that for the Witcher. Don't try to fix what isn't broken.