You already opened a thread about it.
https://forums.ubports.com/topic/6357/why-we-not-change-lock-screen

It has been closed to redirect you to the open topic:
https://forums.ubports.com/topic/6022/login-screen-code-input-design/

There is already work in progress regarding a new lock screen, so you can contribute there.
And you can also check out these projects that might get you what you want:
https://open-store.io/app/uhome.pavelprosto and/or https://open-store.io/app/launchermodular.ubuntouchfr

Multiplying the threads won't help you but it starts to look like spam, so please search the forum prior to posting and read the documentation or threads you're referred to.