This is like dropping support for Internet Explorer 6 in a website - code gets cleaner at the expense of a minor group of users getting a worse experience. I think it is a good tradeoff.
I am happy that they will remove this mode in the future :)
That gives you a buffer you can look through previous commands and use normal-mode commands to edit them.
Also, you don't need Ex mode to edit last commands. You can just press Up from cmdline.