I don't see any reason they should be connected.

Obvious or not, but you didn't mention the game in the title.
No poll either.

but yes

I dont see many No reason diablo games hybrid forums.
In some strange reason moderators are keeping this,
also as you said they putting together Ladder Nonladder and you have to Filter everything now..
More complicated, less effective.

Example:
https://forums.d2jsp.org/index.php?c=6

Each game belongs separated in this section:
https://forums.d2jsp.org/index.php?c=5

But it isnt..

Each game also has to have theyre own subtopics,
legit duelings, trophy rooms, strategy builds..
Simple each game theyre own Section,
same like Diablo3, Immortal and Diablo 4 got ofcourse,
as all are completely different games orcourse.

hell yeah! I was so bummed when they combined them.. it's not very efficient at all

Reading is hard sometimes