What? Which ones? Escape from Tarkov is the most expensive Unity game to run that I know of, and it doesn't have this issue.
The issues with UE5 aren't the base engine. It's Nanite and Lumen, and how easy they make them to just toggle on. Unity doesn't have any features like this. You can get things like them on the store, but they aren't baked in. They do have ECS, which is designed to have a ridiculous number of entities operating at once. I could see how that could cause this issue if unoptimized, but not many games are using it yet so it's not what you're talking about.