TL;DR: So, if you want to create a game with performance in mind, you need to use a game framework (as it does not abstract the code away behind UI elements, and basically just handles raw rendering of objects), create your own engine/framework from scratch or use something that does not focus on features or DX, but raw performance.

I’d guess companies using Unity, UE or other finished third party game engines believe they can just leave everything to the engine, no optimization work required. It’s literally built drag-and-drop like anyway, especially for Unity which basically already has all parts to a working physics and movement system implemented, they just need to be dragged to the objects. And due to that it’s much harder to look at, understand and work with the actual code, especially for optimizing it.
In contrast, companies creating their own engine or using a more low level engine are more successful in my experience. The Metro series is built in 4AGames’ own Engine, the 4AEngine. Metro Exodus runs with 60 FPS, which is perfectly OK for a story game focused on immersion, in 4k and mid quality, on a 1070. Yet the engine does not lack features afaik, raytracing, HDR, PhysX etc. and it supports Windows, Mac, Linux, PS3-PS5, etc.
I believe it just runs better as it was made by the people using it, out of anger about other engines with inferior internal design, and for a specific purpose: Metro.
Games using Source or GoldSrc are obviously more performant, they have less graphical features anyway. Still, a game running at 4k, highest settings, with 200+FPS on a 1070? That is/was CS:GO. Even CS 2 runs with 100+FPS at 4k and mid settings, excluding bugs that are still in the Linux version due to Valves very poor testing/beta decisions. Sources performance comes from it being optimized for HL, Portal, CS etc., so small, closed maps with the ability to split them into many parts.
Both of those have native Linux support in every game, Unity games often don’t.
Games I noticed bad performance with common engines are eg. Raft, which uses Unity, and again runs with 20 FPS max at 4k and highest setting. Mid settings are 60 FPS.
Crusader Kings 3 uses the Clausewitz Engine, which is kinda an exception. Even though it’s built for such a style of games, 2D click games, I had a horrible experience playing it. Again, 4k on a 1070. Zooming in a bit too much causing all symbols of countries etc. to load will make the game drop from ~80 FPS to 20. The netcode is horrible, it is out of sync basically permanently. Though it may be rare to encounter such a problem, it is still part of the quality of an engine and therefore finished game.