Yes, but. And that but is that these entities not only actually and provably exist in D&Dland, but have defined powers and abilities. And again, we don't have stats for gods of any alignment in 5e (the actual god, not just an avatar), but we do have stats for arch-things. So what's the difference between a god and an arch-thing? I don't know.
To move away from Bane and Asmodeus for a moment, gnolls probably consider (inasmuch as they can consider anything) Yeenoghu to be a god--but he's not. He's a demon lord. So back to the main question: what is a god? If it's just a title given to something that's worshiped (or venerated, sacrificed to, whatever), then Yeenoghu--and Asmodeus, and Orcus, and anything else that has followers are gods. If there's something else that differentiates them? Then again, I don't know.
See, Yeenoghu is a perfect example of what I'm talking about though.
He created the gnoll race.
He answers the prayers of the gnolls.
He gifts his followers power.
He sends them signs and omens of the future and of his will.
He can have non-gnoll worshippers who also get sparks of his power.
There is nothing that a god does that Yeengohu doesn't do. Even living in the Abyss isn't a strike against him, because multiple beings labeled as gods make their home in the Abyss.
I think that instead of saying "we don't know the difference", after looking at the increasing lack of differences it may be more accurate to say "there is no difference". Yes, they have been given different titles, but a title alone does not make a difference. Just as a King is no different from a Shah.
Yes, there are benefits to having mortal worshipers. But unlike gods, fiends don't have to rely on them. If their supply of mortal worshipers was completely cut off, they'd be inconvenienced, but they wouldn't die.
Maybe, maybe not. But there are many gods who wouldn't die either. Not all settings have the gods die if they are not worshipped.
They wouldn't ignore it entirely, but I doubt it would be a main target. Unless a handy portal appeared.
But it isn't the main target now either. The main target is Baator, hence the Blood War. Which means that at best, there is no appreciable change in the status quo.
No, of course not. But there's a huge difference between "I don't like these redundancies" and "these redundancies should not exist at all." And you've been leaning towards the latter.
And I say, why not? Sure, they can be annoying, because the average setting doesn't really have room for or need that many types of low Hit Die humanoids, especially if each of them has a culture of their own. But they can also be useful, especially if each of those low Hit Die humanoids has a culture of their own. Same for gods and arch-things. Hell has interesting conflicts--not all of which are actually combative--because of the rivalries of Bane and Asmodeus.
Any of these issues could spill out to the Prime and make for interesting drama. Imagine if you had an elf cleric get looked down upon by fey because he follows Corellon and not the Seelie Court.
See, you are reading into my posts an intent that I have not expressed. Yes, I personally have been removing some of these redundancies, altering the game to fit myself. But I have not been advocating for removing them from the game at large. I have never once said that we should get rid of all evil gods.
All I have done is try to prove that the Evil Gods and the Archfiends taken together is redundant. And therefore, if someone wanted to get rid of the evil gods for their homebrew, they aren't losing anything. Which was the initial question asked "what are we losing" the answer is very much nothing of substantial value.
If you want to argue that they should be left in the game because redundancies are perfectly fine... go ahead? It literally has nothing to do with my argument. My argument is purely about showing that they are redundant.