Analyzing the Issue
Due to the worse performance found in new Minecraft versions, many enterprise servers decide not to update, so they can sustain more players without breaking the bank. They then use plugins like ViaVersion to allow players with newer versions to play.
One of the main cons of older versions is security. Hacked clients can be used to crash servers using modified packets, often using hard to parse packets such as packets with written books. Sadly, most of these issues can't be solved by simply limiting packets per second, but require a more advanced detection system to take more factors into account.

Introducing the LagAssist anti-crasher
Luckily, LagAssist already had the functionality to analyze packets efficiently. With a few tweaks to make the system more efficient (and also protect the server from packets lagging ProtocolLib plugins), it was ready to go.
I've implemented a system to analyze the packet based on its contents, size, and count per second to detect almost any generic crash packet by default.
It also provides a debugging system (to understand how hacks crash the server) and an easy configuration system which means you can add anti-crasher modules as you see fit, without having to learn Java.

(!) NOTE:
The default configuration may still have false positives. It was tested on production on a minigame server at Gamster. A key aspect that may currently cause false drops is large meta items such as tools.