VoidLeech

This mod does technically prevent duping via the blueprints. It unfortunately does that by making the blueprints entirely non-functional.
Specifically, it will rollback any interaction with blueprints where it results in you obtaining more of an item than you had before the interaction. Given that all crafting is to make an item you didn't have before, this rolls back all crafts, even if no duping occurs.

For server owners genuinely in need of a fix, it'd be better to just make a datapack that disables the crafting recipe of the blueprints.

From an adventure standpoint Aquamirae really has it all. Once you've determined you want to engage with it, it is not at all hard to do so: just find a Deep Frozen Ocean, and enter the Ice Maze where you can definitely get lost if you play without maps or coordinates.
The atmosphere here is really good, and you're not just running around to your goal, you really have to pay attention to how you travel, as the water itself, not just the creatures in it, is dangerous.

The structures are challenging but fair, and are still engaging when you're taking on the content in multiplayer. Each comes with unique loot or snippets of information on what else is out there for you to discover and interact with.

The Cordelia boss fight is one of the better boss fights I've seen in this game, and you get a useful piece of armor that I wish was required in more places than just the Ice Maze.
The Eel however is very underwhelming, and its scroll reward is honestly not worth it.

The unique rewards are interesting and not just exclusively useful in the mod's structures, and there's some new plantlife allowing for underwater lighting, which is amazing.

The Ice Maze replaces the Deep Frozen Ocean. I personally like that ocean so that being gone is a bummer, but this is great for the aesthetics of the mod's content itself, and for the 'questline' it basically guarantees you won't have to find another Ice Maze to complete it.

I've always always, eventually, gotten bored of (modded) Minecraft after a while of being excited. That has not been the case since I was shown Create.

Create is a tech mod without black boxes.
It's a tech mod without electricity (I'm sorry FE/RF, I just don't gel with you).
It doesn't really massively outscale any farms you can make in vanilla unless you go crazy.
It is also practically a decoration mod of practical decorations.
No guidebook clutter or need for a wiki, just [W] Ponder.
Trains.

You couldn't nerdsnipe me better.