This is a cool song but it has nothing to do with melodic death metal. That would be bands like (old) In Flames, At the Gates, Amon Amarth or Dark Tranquillity.
First off, I’m not the arbiter of what does and doesn’t belong to a certain genre. That’s, to a certain extent, subjective and people don’t always agree. However, there usually is at least some consensus in the community, otherwise the genre names would be useless.
That said, I personally wouldn’t call this melodic death metal either. Most of the song is just clean singing and clean guitars, both of which are sometimes used in melodeath, but they’re not a defining aspect of it. And even the parts with harsh vocals and distorted guitars are missing the riffs that are typical for the genre. It’s closer to a progressive death metal or groove metal sound similar to Gojira or Opeth.
Overall Jinjer are also definitely not a melodeath band, they’re metalcore, which is often seen as a subgenre of hardcore, not metal, although there are bands that are more on the metal side.
As I said, I’m not the genre police, this is just my opinion. But I think (sub)genre definitions are useful when talking about music and if we start using them too loosely, they lose their meaning and as a result, their utility.
What genres of music do Lemmites enjoy?
Bands suggestions too, curious what folks are into!