Actual merit. I felt like it was an actual journey rather than just a videogame.
I did not like Undertale and I do not see how this game could possibly overlap with that rancid game outside of animallistsic character design.
Hollow Knight is an extremely competent metroidvania, but I strongly believe 9S mogs the shit out of it. Its downs are lower than HK but its highs are ever so much higher.
As far as merits go, if you're interested in what I think was good about it:
Compelling writing
I heabily disagree with its defeatist philosophy, but I believe that outside of my personal views the way the story and the characters were delivered was stellar. I loved the characters, I felt for them, I cried during the end.
Exploration
Secrets aren't overdone, it rarely feels like an obnoxious maze. The maps are compact and don't overstay their welcome, which is an issue even the "ever flawless" Hollow Knight was guilty of.
Combat
Weakest part, to be honest. I think the combat system is heavily flawed but still fun enough to be worth it + the rest of the game carries it. It is parryslop that feels like you're studying for a test rather than battling a powerful enemy, but when you do memorize the patterns, it at least looks cool when you win at a boss fight.
Soundtrack
Not only is it 10.5/10 on its own, it PERFECTLY emphasises the events it accompanies. It builds emotional connections in your brain between the sounds and the happenings extremely well.
Overall
I hate parry slop. I hate metroidvanias. I hate chink aesthetics. I hate games that cost more than 20 dollars (I waited for it to be 40% off). I hate every genre aspect and theme that this game represents. But it became one of my top 10 favorites due to the sheer style and quality of execution as well as the emotional stimulation it gave me. No game has made me as emotional as this one.