The final act in the Party-System era of Ys is a flawed but deeply interesting game.
What I liked:
+ Best writing in the series
Ys IX takes one step further from Ys VIII and delivers the most interesting setting and main story in the franchise's history. Fascinating twists, engaging character writing, I deeply enjoyed seeing the story through to the end.
The localization was also fantastic, extremely good job by NISA after how messy Ys VIII's loc process was.

+ Fantastic movement options and level design
The amount of freedom in the movement in this game is amazing. The dungeons that make use of those options are easily some of my favorites in the series.

+ The music is...good
Is it noticeably worse than Ys VIII? Absolutely. Is it a bad? Hell no. I can listen a good amount of songs from this game that I will keep listening regularly over the years. Hayato Sonoda is the MVP of this soundtrack tho!

What I didn't like:
- The cohesion between gameplay x setting from Ys VIII is severely diminished
Elements brought from YS VIII like raids, barriers to exploration and base building all feel very arbitrary / superficial to Ys IX's setting. Those elements were clearly built with the isolated island setting of VIII in mind, so just pushing it onto a different setting lost a bit of that cohesion.

- Rigid chapter structure
I pondered a bit whether I should include this as a problem or not, because this is an aspect that it's present in almost all Falcom games. The chapters have very predictable structure, slowly building the plot in a way that feels sorta predictable. The writing here is the saving grace, since the twists / mysteries make up for that predictable structure.

- Subpar environmental art direction
Graphics are never a priority for me, but I have to list it here because Ys IX is the perfect example of Falcom's limitations when building dark, atmospheric environments. The game looks drab, lifeless in a way that clearly isn't deliberate. It somehow ends up looking less impressive that PSVita's Ys VIII.

- The problems regarding the combat system in Ys VIII are still here. Nothing was changed or meaningfully improved.

Skill spam? Still there. Overreliance in Flash Guard/Dodge? Still there. Absolutely terrible combat visibility by cluttering a ton of enemies together, just like the raids in Ys VIII? Still there. The Monstrum Gifts are barely useful in combat as well, outside of maybe Crimson Line.

- Knock on Nox is a joke as a final boss theme.

-------------------------

I heard so many negative criticism about this game before playing it, so I'm happy to say it surpassed my expectations, albeit with several problems as well.

I'm of the opinion that the party-system games should've ended in Ys VIII, but I'm glad that Falcom took another shot at it and built a game that feels distinctly different from anything else in the series.

Can't wait for Ys X!