We're working on those things, but we agree the debugging, performance, and iteration time are not in a great place for web today. We have plans for how to fix them, though, and are working on several of them currently. These are mostly under the umbrella of Project Tiny (the team I'm on), whose forum you can find here: https://forum.unity.com/forums/project-tiny.151/

It's very experimental still, and iteration times for web are still not amazing, but we do think we have a way to get them to be actually good, while still letting you write and debug C# as you would expect.