For me the "uv" manager has changed my Python experience because: (1) it has a correct resolver whereas "pip" certainly doesn't and I'm not sure about poetry, (2) it is crazy fast, (3) "uv" is just a binary which I can pip into my system.
(3) is important because if it was written in Javascript or Java or Python or .NET or many other languages I'd have to learn something about the runtimes of those environment to get it working. If it was written in Python it would have to deal with the bootstrapping problem that it ought to have it's own Python installation separate from the one that it is manipulating so it can't have conflicts with that environment. (e.g. how many times have I busted my poetry?) I can use "uv" or "ruff" without learning anything about Rust!
As for (2) the speed of "uv" has as much to do with better algorithms and caching as it does with being in Rust and thus much faster than Python. I think you could have done better than Poetry in Python but "uv" is transformative in that it can often build an environment in seconds or less whereas with "poetry" or "pip" or "conda" I might have time to pound out a few posts on HN. I used to avoid creating new Python environments as much as possible but now it is fast, easy, and even fun.
I bet it is more work to write "uv" in rust as opposed to a similar tool in Python but the impact on the community is so huge because we can finally put problem (1) behind us and do it with speed, reliability and grace. I had notes on how to build a better python package management system and sometimes thought about trying it but I'd become convinced that the social problem of too many people finding half-baked tools like "pip" and "poetry" acceptable was intractable. Thanks to "uv" nobody will ever have to write one.