While I largely agree with your statement, I do find the newly revamped CA site to be an exception. The booking engine is quite functional and the overall UX intuitive. Much better than the likes of MU/CZ/CI/BR. You can definitely make a mixed cabin booking with ease.

Managing bookings is a whole different story however...

Also with calling CA - unless you call the local office during office hour, you get transferred to the Chinese call centre. Then the only way you can pay for anything is via wechat/alipay. Learnt my lesson the hard way after wasting all that time and not being able to pay in the end.