That is untrue, for exemple making a voxel game on unreal is at best a miserable experience. UE isn't a silver bullet.
If it weren't true, then companies would use a single engine for all their games and they would all perform the same. But they don't, which is why they use different engines. Just like you don't use one type of canvas to paint every painting, you use a specific type of canvas for the specific type of painting you wish to paint. Same with games.
When a game engine cannot do or achieve what is required, wanted or needed for a project, they develop one that can or move to one that can. Because games are an ever-inovating breakthrough technology and each one requires an engine that can fulfill the vision of the game's designer within the time they want it in. And it's not just about gameplay reasons, there are so many reasons inside and outside of the scope of the game on why a company would use an engine.
For example with Bethesda games;
- Dishonored 1 using Unreal Engine 3.
- Dishonored 2 using Void Engine.
- Doom 2016 using id Tech 6.
- Doom Eternal using id Tech 7.
- Fallout 3 using Gamebryo Engine.
- Fallout 4 using Creation Engine.
- Starfield using Creation Engine (even though people are by now fed up with it and begging Bethesda to kill this engine off as it is outdated and obsolete)
As for Unreal Engine, it is a terrible engine that is only good for eye candy, at the cost of terrible performance as it's notorious for being a stutterfest whenever it has to load in assets. And Unreal Engine games are for the most part never in-depth complex games, mostly action-adventure games. Unreal Engine is for companies who don't know how to code and optimize to save their life, so they use that engine and their games always suffer as a result. Just because it's popular, doesn't mean it's good. Darksiders 3 (UE4), Star Wars Jedi Fallen Order (UE4), Batman Arkham Knight (UE3) are great games, but also some of the worst performing games due to their stuttering and they're coming from 3 different companies.
So no, I do not think they should use Unreal Engine nor do I think they need to, if their current engine is achieving everything they need it to.
