Not sure what you mean, but that's what Valley of the Drakes feels like to me when you go from Firelink to Blighttone.
That connection actually has the exact opposite effect on me than it seems to have on you. The fact that something so dark and scary can be accessed from a calm place like Firelink in less than two minutes completely takes the atmosphere away from me. It doesn't feel like these places would and should exist so close to each other.
But literally all the places you mentioned have those rapid transitions. That's true for all the souls games.
And this is kinda my point. I think the level design in DS3 is better than in DS1 despite the fact that it it not interconnected, not because of it.
The way you kept saying it made it sound like you thought it was better than DS1 because it wasn't connected:
People fault DS3 for not being interconnected but I prefer DS3 because the larger areas feel interconnected with themselves without having to interconnect with every other area of the game. That's why I think certain DS3 areas viewed as separate entities without the context of the rest of the game are so well designed.
I don't understand why you think this is the case, as there is nothing that makes DS3's level design better that wouldn't allow it to flow naturally into other levels the way DS1 does. It doesn't feel like spit-balling when you keep saying things around that idea.
My point about area transitions is not that it isn't smooth. It's that it is so clearly a Path Between Two Levels. It feels really gamey. It doesn't feel like a real world even remotely. It just feels like I'm walking through a theater set or some weird theme park. Valley of the Drakes doesn't feel like that to me at all. It's a little area on the underside of the cliff beside firelink. I love that. The world is scary and just like the rest of the world, there are small places of respite. Firelink isn't even super safe, considering you literally have a graveyard right there in it with respawning skeletons. Valley of the Drakes isn't even directly connected to firelink. It's just the outside of the cliff that turns into a wall that the city is built on. Blighttown is the a result of the refuse of that city. So when you look down from firelink or other areas of the city wall you can look down and see Blighttown. That helps the world feel bigger because all those places you see are real places that are actually where you see them. You experience them. You go those places. They have physical place in the world. They aren't just nice little pictures. The whole world feels like one great big level. And even so, you have really well designed areas like the undead burg or blighttown that do not take away from that feeling, and only enhance it.
Maybe the transitions are a little quick in a few cases, but again that is the case for Dark Souls 3 as well, but worse. I mean, you literally listed Irythill of the Boreal Valley as a level you liked. That transition is bonkers. You go from this swamp into these tiny catacombs into this sudden snowy winter wonderland. Dark Souls 1 has nothing like that.
Like, how are you going to say oh going down the side of a cliff face...shouldn't be there...? But then you're fine with Irythill's rapid transition.
Lordran is built on a mountain, with its walls jutting up from the cliff faces to take advantages of the cliffs as already natural walls. But as such, you have canyons and paths on the sides of those mountains. Blighttown is within those walls, hence the giant drains. Valley of the drakes is outside those walls on the oppposite side. Pretty natural so far. Firelink shrine is simply a small shrine and graveyard outside of a great big church up on the wall, as a lot of graveyards are. I don't really see what's so weird about that?
And again, even if you think it is weird thematically, there's nothing gamey about it. Everything fits in a really normal way. You have a small shrine on the edge of a cliff. Down below on the side of the cliff are some small drakes, which I guess in this world like to hang out in that kind of area. Up above is the big stately church and township where all the guards have gone undead. Further out past the cliff is a presumably newer township that we don't really visit because there's not too much point in it. But given we can go to all these other places so naturally, most people don't even notice. The fact that most of the scenery is already committed to being physically real already sells the world.