ClassicLFG addon will be blocked in an upcoming patch that will add restrictions to the Classic add-on API that will significantly limit this add-on and others like it.

Thanks Blizzard for this smart move!

Blizzard blue post (Source from Blizzard Forum)

We’ve been closely following the community discussion around this add-on for WoW Classic, as well as analyzing it to make sure we understand how it works. After careful examination, we believe the nature of ClassicLFG is incompatible with our social design for Classic. Thus, in an upcoming patch (in the weeks following launch), we will be adding restrictions to the Classic add-on API that will significantly limit this add-on and others like it.

In line with what we shared at BlizzCon last year, we intend to be very careful about allowing add-on functionality that might undermine aspects of the social dynamics that are core to the Classic experience, even in cases like this where it’s clear that the addon author had no ill intent and was simply trying to provide a service to the Classic community. Ultimately, if a streamlined group-finding system was something we considered compatible with Classic, we would have kept the modern Premade Group Finder tool rather than choosing to remove it from the Classic client.

It’s difficult to articulate a clear-cut rule for exactly when an add-on crosses the line. However, when an add-on goes beyond presenting information or providing aesthetic customization, and attempts to create an interconnected social network that relies on other players also using that same add-on, we are likely to scrutinize it particularly closely.

Source : Blizzard