It's a video game engine. It's got a ton of optimisations and tweaks to make it run in realtime, but if you're making a movie there's no reason not to spend hours rendering each frame. You don't need to optimise meshes at a distance, or use real-time raytracing with noise reduction rather than just simulating a thousand bounces or limit yourself to 4K textures, you can use as many particle effects and simulations as…
>> It's got a ton of optimisations and tweaks to make it run in realtime, but if you're making a movie there's no reason not to spend hours rendering each frame. That's how it's used though? It only runs real time for preview, but the final product is very much not rendered in real time at all. Obviously it's a very flexible tool that works with what you need and what you can afford - Disney runs it on their compute…
My issue with UE is the opposite, the engine went too far into cinema production, and making it a performant game engine requires code refactoring. At which point an open-source engine might be a better choice. Its a mix of two (three) worlds, and not the best choice for one specific use.
For what is actually hard to do, like character animation, UE is a good choice. The lighting can be replaced more easily than the animation system.