"Shared with Us" link in Modern SharePoint Menu (behavior)?

I get all of your frustrations over this, but the assertion that it's a (universally) "USELESS" feature is not objectively true. It may be useless for you or your users, but there are absolutely valid use cases for it. As an example, I work at a large university and occasionally help out with the team that handles mass-mailings to the university community. The folks requesting those mailings often share files with the team (the contents of the message, attachments to include, recipient lists, etc.). Since it's a "Team" the group mailbox (where that share notification and corresponding link are sent) is not readily available/convenient to get to. Therefore, having a single URL to that "Shared with us" view makes it really easy* for the members of that team to access those files.

*My personal frustration with this "feature" is not its mere existence, but rather the inconsistency of it. That is, sometimes it works as expected and shows the files/folders that have been shared with the team, but sometimes it shows nothing at all. Or, shows some files, but not newly/recently shared files. In other words, I'm more annoyed by the fact that it doesn't work all the time.

That being said, I totally understand that in many organizations, you might not want it to appear. I think the most balanced way to achieve that is to have a setting (in the SharePoint site settings for each group-connected site or in the Group settings page) where an owner can toggle it off (e.g.: a checkbox labeled "Show Shared with us link in Quick launch")