Am I missing this, or is there no way to turn on the ability for users to ignore/block other users?
... not by a normal user.
Is this a thing anyone want to be in an near update?
I know only one forum software, that had an implementation of a ignore list and that didn't work well. Because of that, the feature was removed in the end.
This forum software structures the entries in a threaded way with branchings, where needed. This means, that a reply C to a reply B is handled as a reply to the specified entry (B) which may be a reply to another one (A as the initial post or another one). The first mentioned reply (C) is not necessarily the reply to the original post (A) that started the conversation. That way the forum software builds the branched structure, one can see in the overview page of this forum. With this logical structure the script would have to build a tree of entries with inexplicable gaps in it (for the entries of blocked users) or it would have to show for single users unreachable entries (again: for the entries of blocked users). That would be the first problem.
The second problem would be, that the content of entries of blocked users could be accessible as quotes in entries of not blocked users because in their entries the logical relation to the source of the content in the entry of the blocked user can not be made.
In contrast to this in a bulletin board every reply is a reply to the initial post. There are no branchings. This is similar to messages and reactions in many social media systems. The script would be able to block the complete thread, when it was initialised by a blocked user or could block a single reply, made by a blocked user. There would be no logical gaps (no problem number one). But also there the second problem with quotes is not avoidable.
As stated by Micha a forum is a medium, where entries a related to their predecessors in a strong manner. A blocking feature would be really difficult to implement and there are a lot of things you can do wrong. And at the end some people would like to have things implemented differently and other people would strongly disagree. IMHO it's a minefield.
Trenne niemals Müll, denn er hat nur eine Silbe!