Mr. Atara said it best with his review which i'll put here: https://gtm.you1.cn/id/atara1/recommended/2919560/

TLDR: if you go into this game expecting the first one you are going to be disappointed.

The first Idle Caliber was a hidden gem—rough around the edges, but ultimately rewarding once you took the time to understand its mechanics. While it wasn't immediately clear what was going on when I first played, once I familiarized myself with the system, everything clicked, and the hours melted away.
Unfortunately, this isn't the case with Idle Caliber Zero.

One of my biggest issues is the user interface. It's a more modern, soulless design with plenty of sharp edges that feels like it was made exclusively to break free of any RPG-maker assets. On top of that, it frequently fails to function properly, especially in the main menu, which undermines the user experience. (To elaborate, i think certain menu options are bound to left and right click and i found myself constantly trying to close the different widgets before being able to navigate away)

The combat system has lost all of its originality. What was previously a chaotic auto-battler with no upper limit is now the same generic, soulless, turn-based RPG combat system featured in every dime-a-dozen RPG under the sun.

Another problem is the unnecessary tabletop RPG mechanics—such as dice rolls, saving throws, and success/failure checks—that complicate gameplay rather than enhance it. There's a way to implement this, I just don't think it has any synergy with what you have on the table already.

The inclusion of dating sim elements also feels forced and underdeveloped. The character "chats" appear to be AI generated using a server that was cobbled together. The kissing option is extremely unsettling, and the option to "sleep with" certain characters is disappointing—essentially just a single, sfw CG image paired with some brief dialogue. Despite some passable character designs, I simply don't feel any connection to these characters.

Then there's the day-one DLC, which is self explanatory. It consists of character wallpapers for the main menu. These are literally just paywalled wallpapers ripped from Wallpaper Engine. While the art is fine, it adds no real value to the game, and paying for it feels like a cash grab—which is overall just plain disappointing.

One of the features of the first idle caliber game that was praised by reviewers was the gacha system. Although it hasn't been removed, it has been completely reworked and it is no longer satisfying to roll for new characters. For each roll you get to select between 3 characters or the ability to re-roll which doesn't feel rewarding at all.

In fact, much of the game gives off the impression that it’s AI-generated—especially the scenic backgrounds, which can feel almost uncanny, as if the AI wasn't quite sure how fast a windmill should be spinning.

All in all, Idle Caliber Zero is a step backward from its predecessor. The game's design choices, frustrating mechanics, and lackluster content leave a lot to be desired.

⭐⭐