It is also important to note that this is not specific to Zed. As someone else have mentioned, it is a cultural problem. I picked Zed as an example because that is what I compiled the last time, but it is definitely not limited to Zed. There are many Rust projects that pull in over 1000 dependencies and they do much less than Zed.
Edit: Ghostty is a good counter-example that is open source. https://github.com/ghostty-org/ghostty/tree/main/pkg