I can understand how people can be upset with Evelyn Parker dying. The player is introduced to Parker early, and her introduction helps to set the tone of the beginning of the game, where you're supposed to feel hopeful (i.e., getting rich/famous in Night City). Parker herself is charismatic and intriguing, which leaves the player wondering what exactly her motives are. Unfortunately, before you can learn more from her, she disappears and eventually dies.
However, I don't agree with people assuming it's because content was cut from her character. It's always seemed clear to me that she serves as a narrative mirror to V; that is, someone else who is seduced by the "City of Dreams" and eventually falls victim to it. Parker tries to carve out her success, but she does so by betraying or making back deals with everyone she's involved with.
For example, the moment you're introduced to her you find out that she's planning to steal from Yorinobu (someone she's intimate with), and that same evening, she tempts you to betray Dex, your fixer at the time. Later you find out that she was going behind the Voodoo Boys to deal with Netwatch, which is likely why she was attacked by the Voodoo Boys. Finally, if you read the email she sends to Netwatch, one of her requests is for protection and a new identity, suggesting that she was probably going to skip town and ditch you as well. I can empathize with her because through her and Judy's dialogue it's clear that she's just trying to find a way to survive, but her betrayals and back dealings have unfortunate consequences.
Her death is also integral to Judy's storyline. Up until it's confirmed that something has happened to Parker, Judy remains stagnant working for the Mox (she later confides to you that she's depressed during that time frame). When Parker commits suicide, it finally stirs Judy to action. The whole reason Judy joined the Mox is because she thought they would fix Night City, so when Parker dies, she finally tries to take matters into her own hands. Unfortunately her attempts don't have a happy ending, which becomes the final push for Judy to realize that she needs to leave Night City.
So yes, while Evelyn Parker unfortunately dies early, her impact is significant, both to Judy, and to one of the overall themes of the game. Of course, I'm not saying that the writers never changed her story, it's completely possible. However, from a narrative perspective, I can easily see why Parker's storyline played out the way it did. The fact that people to this day wish that Evelyn Parker survived is a testament that CDPR makes some great characters.