Lazy DataFixerUpper (LazyDFU) – accelerating the launch of minecraft [1.17.1] [1.16.5]

The Lazy DataFixerUpper mod, aka LazyDFU, is a mod that optimizes and accelerates the launch of minecraft, with it the game will load faster, especially on weak computers. The mod disables the resource-intensive operation of loading functions related to converting worlds from older versions of the game to new ones.

These functions are used when transferring worlds created in old versions – to newer ones, these functions are loaded at the start of the game, on powerful computers it takes 5-10 seconds, and on weak computers up to 50 seconds. This mod disables the loading of these functions, because converting worlds is rarely required, and if you run an older world, the game will first load the conversion functions, and then convert the world, that is, you will have to wait.

Provided that most players do not convert worlds every time they launch, this mod is more than useful, especially on slower PCs. 

Demonstration of the difference:

Above is the launch of the game on AMD Ryzen 9 3900x + 32 Gb RAM, on the left without a mod, on the right with a mod.
Below is the launch of the game on a laptop with Intel i5-8250U + 24 Gb Ram, on the left without a mod, on the right with a mod, after the visual launch of the game on the left, the processor continues to be loaded at 100% for some time.