Boost 1.87.0 (specifically ASIO 1.33¹) breaks https://github.com/zaphoyd/websocketpp by removing io_service and more (yes, I know about Boost.Beast).

It would be great if deprecated things were annotated with [[deprecated]] so one can get compiler warnings before the things are removed. If this gets too noisy, users could define BOOST_ASIO_NO_DEPRECATION_WARNINGS² or something similar. Explicitly opting out is much better than requiring opt-in. I'm okay with removing stuff in minor releases³, but it's important to actively notify users about it - expecting users to use BOOST_ASIO_NO_DEPRECATED or to actively check the documentation for all their used functions is not enough in my opinion, we have [[deprecated]] for a reason.