There have been some good adaptations though, even ones that did their own thing - like Foundation.

Most of human history has been this way. People telling and re-telling their own fanfiction or alternate versions of everything from Greek tragedies to the Bible to everything else.

There have been good adaptations. The Castlevania anime was great. The first one at least.

I think the bigger issue is the trend of putting a lot of money and effort into season 1 to make a good impression and try to get loyal fans, then to take all the money out for subsequent seasons and hope the fans stick around.

It's interesting that you mention the Witcher because I thought season 1 was way better than anything the games did. I could see how the structure in particular might not be for everyone. After season 1 it's obvious that everything went cheap- the lighting, the costumes, the makeup, the locations, the editing, the sound design, the CG effects, the writing. I normally don't even have an appreciation for costume design, but by season 3 it looked like they went to Spirit for Geralt's armor and Kohl's for Yennifer's dresses.

Arcane was another one. Season 1 was way better than anything League of Legends did during the few years I played. Season 2 was still... Okay, but the writing was terrible. The backgrounds went from detailed panoramas of piltover to just stylized colored fog. A lot of the characters seem to do things that go against their previously established motives or just do things that don't actually make sense but are required to move the plot along.

To bring it back to Castlevania- after the original series, the Nocturne series felt like a cheap knockoff. Which was a real shame because it was the same studio and I really enjoyed most of their other work.

Castlevania is fucking sick tho. Watchmen the series is arguably equivalent to the OG comic in terms of writing and artistic quality.

There are genuinely great adaptations out there.