It all lies in the engine of RUST itself and in the level of curvature of the Facepunch arms.
First you need to understand what the engine is and where the legs grow from.
The engine in the usual sense of the word is just a set of tools and a restriction on their use.
As an example, you cannot use a Phillips screwdriver to use a flat bolt.
Facepunch initially chose the free public Unity for their project as a beggar studio in 2013, which is a great choice for games without a budget and all other indie projects.
Unity at the time of 2013 was based on the DirectX 11 and OpenGL versions of the API that were current at that time.
Due to the peculiarities of frame construction in DirectX 11, we have the fact that with a huge number of objects in the frame and / or high details, they cannot be quickly built and sent for rendering by 1 mathematical processor core.
This is where the roots of all problems grow.
Problem # 1:
Facepunch on a rocket arrived from a fired project, they decided to redraw the game for modern realities, hammering on the limitations of the engine, which rests on the features of building a frame with 1 core and wildly overestimated the number of draw calls in a frame at one point in time.
Because of this, multi-core processors work extremely ineffectively at the level of their younger 2-4 nuclear counterparts.
Problem # 2:
It is IMPOSSIBLE to solve these restrictions.
No amount of HDRP will save RUST.
To transfer the game to a new engine with a more adequate frame construction, for example DirectX12, or to the most modern Vulkan at the moment, you need to actually write the game from scratch !!!
To understand the full size of the work for this rather ambitious update, try the following:
Assemble a stool using wood and glue, and then take such a stool, disassemble and try to assemble a new stool from pieces of wood and nails.
In fact, you have created a new stool.
Everything is exactly the same with game development.
Facepunch is more profitable to invest in the creation of a new game, albeit under the RUST 2 brand, and collect the cash register twice, than to pick the actual dead, ending the life cycle of the old RUST project.
You need to understand that RUST will never run normally on weak processors and work efficiently on multi-cores.
No update can fix this jamb, which was originally laid down in 2013 and brought to the absolute much later.
We just have to play what they give us and wait for Facepunch to decide to release RUST2 from scratch, laying a high-quality foundation using modern development tools.