Thread:Sannse/@comment-32125535-20200827235249/@comment-1038387-20200828064149

To address yout bullet points:
 * The new walls don't work on MediaWiki, is the normal welcome system doesn't work. They ahven't implemented a new system yet. AFAIK, it's planned.
 * I've heard some reports that people don't see their messages from Legacy wikis on UCP wikis, but this seems to be a problem that's solved once everyone shifts to UCP. UCP is changed per wiki basis, there's no setting you have to or can switch.
 * Achievements will receive further updates.

Bugs are infuriating, but bugs are part of any new software and there will be updates. It's not a style, and it's not a 1:1 conversion. As for why the change was made, see this blog.