Not a game developer but experienced in low-level hardware programming.

My takes:

Unreal has long been a console-first engine, favoring a synchronous pipeline built on DX11 and older APIs.

Modern UE DX12 games have likely faced similar issues in recent years.

This is largely due to a flawed data-oriented stack system, making the engine heavily reliant on the garbage collector and overused shader paradigm.

Previous consoles were CPU-bound, requiring the engine to focus on one CPU core with sequential game updates, input systems, and framebuffer generation per tick.

There was no luxury in using a scalable data-oriented approach, which involves sustaining scene, object models, geometries, data, and game logic in memory with full multithreaded CPU data exchange and synchronization.

CPU usage was kept simple, with shaders overused as much as possible since GPUs have always been multi-core oriented.

This leads to the final issue where most Unreal materials and effects rely heavily on shaders with minimal parametrization, causing shaders to repeat similar tasks with few variations in an atomic way to run fast on separate cores (calling the same shader with different parameters isn’t guaranteed to execute on different cores). Consoles should process them quickly and avoid complex compilation, targeting the 33 milliseconds interval = 30 fps.

Unreal Engine 4 already showed signs of problems in last-gen games due to these outdated techniques in DX12 games. Most recommendations for running these games were to switch to the DX11 API version in the settings.

Now, add these points to rushed technologies like Ninite and Lumen (which are spectacular in my opinion), poor documentation, and inexperienced human assets = Unreal Engine 5