It's very easy to blame 4Kids for some of the worst dubbing ever but it didn't kill an entire genre like Card Captor Sakura's did, this Otaku Insight will explain the reasons why.

1. Nelvana had the dub and localisation rights.
A common mistake to make with Card Captor Sakura is where the dubbing came from, well it was Canadian dubbed same as Sailor Moon but was also Canadian localized, Nelvana only has two other anime on it's books, Medabots and Beyblade, both were easier to market than Card Captor Sakura because they were both toys first.
2. They tried to market it more to boys.
Anime as a whole was very much a boys thing thanks to Dragonballz with Sailor Moon being the most obvious for girls anime around at the time, with Sakura being joined by Syaoran they tried to market him more as the lead which only made it more confusing in the localisation's narrative.
3. Nelvana had no idea what to do with the LGBT content.
More confusing changes included making Ruby Moon female and struggling to properly translate the more obvious gay moments especially the sexual tension between Touya and Yukito, as well as Tomoyo's massive crush on Sakura.
4. The show was spoiled by trailers.
Yue, a spoiler character was shown in the trailer which I immediately figured out was Yukito, spoiled the plot for me.
5. It caused the failure of the Magical Girl genre in the West.
When it failed to find an audience, it took the genre with it, Tokyo Mew Mew managed to finish but Pretty Cure and Mermaid Melody had two cancelled dubs now lost media, it also contributed to the failure of Escaflowne but that's another story, it would be nearly two decades before another attempt was made with the ill fated Glitter Force but by then the old localisation methods weren't really acceptable anymore, unless you're deconstructing the genre or Sailor Moon don't expect magical girl shows to ever come back.
6. Ironically it would succeed now.
Disney kick started the female lead trend with Kim Possible and two decades later, the majority of cartoons are female led with more open themes of LGBT that Card Captor Sakura had all along, this makes the anime ahead of it's time.
7. Card Captor Sakura is still special regardless.
Despite the poor localisation it's still beloved by myself and alot of 30+ otaku, watching it felt like taking the next step in the fandom especially in the original Japanese.
That's a brief look at Card Captor Sakura's botched dub release, I've got loads more stories from that era but I'll let you choose.
"Escaflowne's messed up history"
Or
"How Gundam got it's groove back and lost it again"
Or
"The Enigma of Hamtaro's Success"
Or
"The Curious Case of Shinzo"
Or
"I thought I dreamt Strange Dawn"
Or
"Did anyone watch Flint the Time Detective?"
Or
"Did Yokai Watch really happen?"