When game developing you dont really optimise untill you have added all the core features and assets otherwise you constantly redoing things. Could they get better performance at this point sure, but yer performance vs all the things they want to do is a forever battle
I am a unreal engine dev, so im just speaking from first hand that 'performance' is a bastard. You think its fine but then its not, or you think you did enough but you didnt ect. The amount of hours you can pour into optimisation and it still runs kinda meh.
If it is not possible to optimize as you go, that is another point for Unity and another demerit for UE. Cause Unity has no problem with optimizing during development, if you know how.
The general problem with UE and UE games in here is that 90% of the games developed with UE are developed by people who seriously should have chosen Unity, because it is just a bit easier to grasp. And, with the right assets and graphical choices, Unity can technically supersede Unreal simply because it is much more flexible - you can install other rendering engines, fx Octane, which UE did support in 4.22 but likely not in 5.x, also it is tedious because the plugin must be compiled for that specific Unreal Engine version, and it is a bitch to get to work, while in Unity you just install the asset. You can extend such functionality
That they decided to fundamentally change the engine for Unreal engine 5 is another idiotic move that makes a lot of stuff incompatible. I directly compare this with being totally disrespectful and disregarding the userbase. Generally, no issues arise when moving to a newer Unity version, so there's also that which they understand how to do.
Unreal is a great tool, no doubt, if you have the manpower and funds to actually use it as it is meant to be used. The problem is that most small-time developers aren't aware of this, which is why most of the games we see in here (including the bigger ones) are awfully unoptimized. For example, there is a game taking up 6 GB but everything in it is stylized and almost without textures. That game shouldn't take up more than 1-1.5 GB. Another example is a game with one house and a few characters, it is bigger than 10 GB.
And if those textures, models etc. cannot be properly optimized when importing them, and the game files aren't optimized and compressed, it tells a lot about Unreal Engine.
It doesn't help that a game usually looks better if it's not really worth playing, which is the issue with two out of three Unreal games in here. Being both 2D and 3D, Unity wins the flexibility battle too. (Check out professional review where Unity gets 10 pros and two cons, Unreal gets four pros and 15 cons!)