Well, during that era of games, you could saw the weirdest, most obscure shit such as Art Truck Battle (from Human Entertainment, Affect and Spike) get several sequels out on PS1. So having more than one game in your series doesn't mean that it's individual elements will remain distinctive enough and non-generic 30 years later.
I'd argue that the striking art direction from the 2023 teaser trailer is the single, most remarkable thing about the entire Marathon IP up to this point, sitting way on top of anything that was done back in the day as part of the original trilogy of games -- of which the oxygen system might be the most notable, that being the reason why it sits at the very core of the new Marathon's design, as a risk-reward dynamic (as well as a timer) in the context of it's extraction shooter structure.
So, hey, the new Marathon is indeed a Marathon game after all.