The short of it

Project Ozone 3 looks to echo the success of it's direct predecessors as well as contemporaries in the Skyblock subcategory but falls short due to simultaneous over and under tuning of core mechanics.

The long of it

Gameplay - (don't waste your time on me you're already the voice inside my head)
There is an innate problem with a lot of modpacks that seek to find the much fabled "perfect pace of progression". That sought after feeling that you're making good progress but not too fast. That problem being, that in order to slow down the ever acceleration found in Vanilla Minecraft where you can go from sticks and stones to diamonds in under an hour, mods often set limitations and extra steps in order to bring us down to a leisurely speed. That's admirable to try to do but the truth is, incredibly difficult to get right. Most modpacks feel like they are just wasting your time, perpetually spinning the wheels like a drag car right before the race. Unfortunately, Ozone 3 is no exception.

Example? The early game starts off familiar but strong. All our old pals are here! Here comes that rascal Ex Nihilo. Oh and look it's Tinkerer's Workshop! And oh my! We're using composters to make dirt. How quaint and familiar. Then we hit the wall. We realize, hang on...yes I'm using all these familiar faces but is there no other paths? No. There aren't. There is no other way to get diamonds other than Ex Nihilo so have fun with the loot table. Tinkerer's Workshop's smeltery is now behind a porcelain smeltery which takes the better part of a Lord of the Rings film (extended of course) to actually make the bricks for the real smeltery and guess what? There is literally no other way to produce dirt for the first 10 or so hours. I'm not joking, composters only, so better get those hoppers and leaves farms ready. These are all in place to prevent that priorly mentioned super acceleration but instead of giving a rewarding feeling of progress it comes across more so as enforced dilly dallying.

I know it sounds like I despise this Modpack's gameplay but I didn't. I just can't ignore the amount of times it made me roll my eyes. Perhaps the best indicator of this is the faithful iron bucket. In vanilla minecraft this costs three iron ingots. In Ozone 3 this costs three iron ingots. However, whereas you can just instantly craft this in Vanilla. In Ozone 3 you need to turn the ingots into plats by manually smashing them at a seperate block with a hammer. There is no additional resources used, no challenge in the station needed to be crafted to make the plates, it just takes time. 3 seconds in vanilla but 30 seconds in Ozone 3 with no test other than on your patience. Tedium for the sake of it.

Aesthetics - It's 1.12.2 what do you expect.
It looks good. Like 1.12.2 has always looked you know? I'd call it a fond memory. There are no grand sweeping changes to any of the textures of the included mods and even though there is something janky stuff in the tokens you get from quests having a rather bizarre texture. There is nothing bad nor nothing exceptional here. It just is.

Performance - Nearly as much waiting as in the gameplay
This modpack runs horribly. Very odd thing considering there is no way this can be more intensive than Meatballcraft but somehow it is? It takes longer to initialize, is more prone to frame drops yet is distinctively less ambitious busy as it's well known for being intensive, 1.12.2 competitor. Very odd. It doesn't crash or shoot my dog so I suppose it cannot warrant a 1 star but I simply don't understand why it's such a heavy breather.