That is reasonable though if a missing feature is trivially obvious must-have. Browsers (and standards, and platforms) that are slow to add it must develop themselves better. It’s nice to respect compat if a new way is a redesign based on feedback, e.g. you used poll/select and now it’s epoll/kqueue/iocp with a fallback. But if it is a feature that was simply missing for years, e.g. UIKit adding random useful methods which existed since forever in Cocoa, no respect. Really, you don’t want to support a platform that takes years to wake up. Let their users know that it’s obsolete, they will update.