That's generally true of most things in Wayland. It's poorly designed and then badly implemented, by multiple different compositors in different ways, leading to endless bug reports and broken software.
About copy/paste in particular, I have solved it for myself because I work almost exclusively in the terminal and the browser, both of which stay running all the time and therefore acts as a clipboard manager for any copy/paste that happens in it. I am just waiting for my terminal of choice to get support for copy/pasting arbitrary mime types, which its maintainer has said he is going to implement.