Since this announcement (Dec 2019), I've been waiting for some information about how this transition would be done. So I receive the notifications, I come here, I see "the new platform is amazing, it'll be new wikis for now, yada yada..." Nothing about the forums.
Last wiki, trying to solve another issue, I had to create another account. I end up remarking that new users have a different view of the top navigation menu.
I've tried to remove that mutant link (with the special ability to hide itself from new users), and create through the nav menu a healthy link (that everybody could see). This worked on desktop, but on mobile, a regular link to Special:Forum generates a disgusting bizarre creature link with an annoying non-sense popup. I've fixed this with a full https link.
I've fixed my problem but I'm still unhappy, because our communication tool is being retired while no replacement has been presented to us, and no information is given either. So I'm sad to say that this situation gives me a bad feeling on what is to come.
Do you have a question or are you just commenting? The difference in the top navigation is due to the default landing page. The links change depending on which page a user has set as their lading page. As for replacing Forum, there have been many different threads about this ever since Discussions was released. I believe this is the most recent one.
Since I've created my account, I've never changed that setting, and I had the Forum link. New users come now to the platform without the link to the Forum, and with a redundant link to the Main Page. That's the matter. Having an option on the preferences makes no difference in this case, as I won't tell every new user: Hey, man, you can have a good link there on your nav menu, just go to your preferences! It's unpractical.
Fandom changed the default for new accounts to Discussions. That is why new accounts have the link to the home page instead of the link to Discussions. This was announced back in April 2019 (see here). A decent number of wikis have already disabled Forum in exchange for Discussions and new wikis don't have a choice. The home page link is redundant only if the wiki does not yet use Discussions (as is the case for Community Central). Fandom recently released the new platform and wikis will be gradually migrated to it. Part of the migration process is removing Forum and enabling Discussions. Therefore, by the end of the migration process, there won't be any wiki on which the home page link is redundant.