I have great memories of oqueue and I think it was really needed at the time to fill the roles in groups for Normal and Heroic raids, as well as more serious pvp, that one ran into playing on certain servers or in timezones. While classic isnt cross realm, i still see the main feature of listing groups with a visual interface as a step way beyond the current lfg spam relay. I think Oqueue could still serve the wow classic community as such and I hope its return will help make pugs much more easier, especially in pvp. At oqueues peak, your group listed and you had up to dozens of people waitlisting.
Currently Oqueue classic looks very much like a port over to classic, but with some lingering connections to features and content not yet in the game. However, there are a few quick edits that will make this addon cleaned up for classic. First in the create a group interface there are still options for "looking for" Death knights and Monks. They should be removed or at least hidden. There are also options for looking for Paladins and Shamans, but perhaps just make it one single option that means either/or for classic (that is more minor).
In the Group type, there is no options for a PvP raid or group, either World PvP or Battlegrounds (wsg, ab, or av).
In the Raid list, all the raids through mop are listed; remove or hide all the raids that are not in classic. In the Sub type you can make group sizes and difficulties that are not used in classic. Maybe just have a simple Raid and party option.
Since crossrealm mesh is not supported, remove battle tag references from interface for this classic (Lite) version.