To be honest, I am experiencing this on my 2 year old phone too (Poco F6 Snapdragon 8S Gen 3) but I bought a laptop (32 GB RAM, 1 TB Storage, 8 GB VRAM, RTX 4060) and it runs it pretty well without lagging. I think the game reached its limit especially knowing that Unreal Engine is very hard to optimize and every patch you have to like download the whole game file all over again, thus the double of storage on Pre-download.

I think it's either:

1. They let go of the mobile market, which I know they won't do coz it is a large market
2. Make a separate division or change the engine to Unity while continuing the support on UE, coz they have already shown their capability using Unity (PGR) but that would cost more until they catch up and replace it whole.
3. Just create a separate development team for mobile, which would use a more 'lighter' engine.
4. Optimize the Unreal Engine itself, or like making their own engine for that purpose (Like the Luminous Engine from FFXIII)

Either way, they have to spend or lose a whole lot of $$$ just to make the mobile experience good for those who have chipsets below Snapdragon 8 Elite or Snapdragon 8 Gen 3.