This is Death being called "Shinigami" on the very first Castlevania. This repeats on the sequels.
There is another japanese word to mean Death in the more European "Grim Reaper" sense. When IGA got hold of Castlevania back on SotN, Death was renamed "デス (Desu)", the aforementioned word for "Death" in kana. Katakana is used when a foreign word (and quite possibly its intent) is transcripted into Japanese.
If anything, IGA initially made Death into the more european counterpart, not the contrary. It is clear, however, that "Shinigami" was the original intent -- which is most likely the reason why IGA returned "Death" to "Shinigami".
It's an agent of the natural force of Death without actually
being that force itself. It causes death because that is its purpose, ergo it's the non-Japanese equivalent to a Shinigami. Death is just a very powerful one of these, that happens to resemble the European lore of Death as a reaper. The European Reaper is not unanimously described as
the singular force of Death personified--there's nothing in any European lore dictating that it cannot simply be a skeletal entity that acts as a middleman agent of the force-of-nature aspect of death.
It's really not all that complicated, really.
We need to stop putting everything we dislike on IGA's account.
A better phrasing would be "we really need to stop creating problems that aren't there to justify shitting on someone we don't like, and simply be content to dislike them of our own volition rather than fabricate reasons to do so."