I understand this not as objects are missing, after all, struct with methods and traits are objects aren't they? But more like the lack of hierarchical inheritance, that is most often used in OOP to conveniently share common code with added specialization. Override only the methods you want. You can do it with Traits of course, but it's much more verbose. You can technically use the defer trait to simulate a sort of method inheritance, but it is frowned upon as it should be reserved for smart-pointer like objects (so the doc says).
That's about what I was going to say. Traits have no data of their own. If you need that, you have to construct it, with a data object in each trait instance and access functions for it. It turns the notion of inheritance inside out. Awkward enough that it's only done if absolutely necessary.
I'm from the C# world and am working through learning Rust... in C# we've largely moved away from using inheritance. Not sure that it's a good thing but "best practise" results in serialisation being implemented differently (serialisers which use attributes, or for more advanced teams serialisation wired in at compile time targeted by attributes - advantage here being that the state doesn't have to be public).
I still use inheritance in C# although it is only used for is-a relationships and those aren't that common. But when you need it for that, it's usually pretty important.
I also think it's much more common to see it in library / framework code and not in application code.
UI in Rust without inheritance is tricky. There's still no great UI framework written in Rust yet, though not for lack of trying! I'm interested to see how Bevy's UI turns out. They're currently exploring the design space and requirements for production-grade UI, actually.
Wouldn’t something akin to swift UI work well in this situation? I can understand that not having a “component” class to inherit would make building custom components difficult, but if most layout and skinning can be accomplish via functions then you can sidestep the issue for most cases I think…
