Repeatedly stating that something is true doesn't make it true, and trying to insist that the Neath is R'lyeh makes it seem like you lack more than a cursory familiarity with either setting. They both feature water pretty heavily, contain very different forms of 'cosmic' entity, and have a certain wonkiness of reality. That's about all the settings have in common.
Well the only difference between the Ryleh and the Undersea is specifically...
The Entrance to Ryleh is in the USA... and the entrance to the Undersea is around Europe.
-Edit: Actually that isn't true... there is a entrance to Ryleh around... Europe... so... huh... Sorry it was a last second detail in a book... Mostly to set up a "But the problem still exists"
A lot of the details are shockingly similar with the differences mostly stemming from the fact that people are actively exploring the Undersea as opposed to the Lovecraft tale where it is mostly secret. Which explains most of the differences (with most of the creatures being displaced). For example how people age in the undersea, is very similar to how it occurs in Ryleh. (it comes off as almost an alternate history)
As well "Cosmic Entity, Cosmic Entity, Cosmic Entity" is honestly the LAST thing I use to compare something. It is storytelling that is the most important. I mean Conan the Barbarian takes place in a Lovecraft universe with lovecraftian entities existing in it... But the story isn't lovecraftian.
For example "Alone in the Dark" is lovecraftian and no real Cosmic Entity is involved... though their presence is felt.
I also tend not to go entirely towards creatures as well, at least in design. Tentacles is often the lazy way to make a lovecraftian story (Hey people! Lovecraft had stories that didn't have ANY sea creatures...)
That's about all the settings have in common.
Well there is how investigation is done (a common trope that the more investigative lovecraft games use), The slow subtle corruption, the peddling of secrets, the "I've seen too much" that sometimes pops in, the tangible phobia. Heck... "Secrets" is a currency, a basic trope of lovecraft games.
Yada yada.
The overall set up, atmosphere, and how things are done... Are very lovecraftian.
Mind you a reason for this is because Londonesk writing (I don't have a good word for this... Think a Dark Sherlock Title mixed with Pride and Prejudice) and Lovecraftian writing share a lot in common. To the extent that I've often mentally projected England onto some of Lovecraft's work.
Other than Ryleh, which honestly if it is a coincidence it is an IMPRESSIVE coincidence... and yeah the creator might not have been intending to go with Lovecraft... But when you have the formula down, it doesn't matter.
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Or rather... "Lovecraftian" isn't whether or not a piece of work manages to have their version of Cthulhu or squid monsters.