However, the plugin system is on its way. There is a demo here. That being said, there is no eta for the plugin system. I think you should not make a decision thinking it will be available in the next month.
I turns out I feel comfortable working with nothing more than the (fuzzy) file picker and stopped using a file tree long ago even in other editors. I like having nothing but code in front of me. Also, thanks to rust-analyzer, it’s possible to create files for new modules using a code action (mod mymodule + code action => create file mymodule.rs / or create file mymodule/mod.rs). However, it’s true that Helix will not help much if you’re going to create and move around a lot of files frequently. In such cases, I open a new shell in another terminal and type commands directly there or use a dedicated tool such as broot. I’m using a tiling window manager, so this is all very straightforward and natural operations. I think this workflow could be improved in a few ways if I could integrate more tools directly into Helix, but I don’t feel less productive than I used to be with vim/neovim/emacs/kakoune previously. This is likely due to the fact that these other "file system heavy" tasks are not what I need to do the most in my day-to-day. It also helps that Rust tooling is very friendly to such setups. When I need to write C# code the experience is not so fun. (At least, I didn’t try to use Helix too much in big C# codebases so far, but maybe it can be tuned further.) This is for reasons unrelated to the absence of a file tree however.
How many crates are you dealing with in your workspace? In my experience, I can navigate within a crate fine using IntelliJ/VIM keys, but when dealing with lots (50+) crates in a workspace, I really want a filetree.