... which does put both cars and bicycles in the same queue, but doesn't eliminate the copy-paste for each new type completely; 'car' and 'bicycle' still wind up with separate 'get_speed' impls, which are textually identical aside from the type names.

Sure, traits talk about functions, not properties/ strict fields, so you need to provide trivial getters if you want to abstract over properties.

True, but not that interesting? Sure we could have some Ruby :get_attrs magic or whatever.

Usually the way people solve this in Rust is with macros.