ECS = Entity Component System. DOTS = Data Oriented Tech Stack, which is the new implementation of ECS in Unity.
Current KSP is plagued by performance issues during advanced gameplay, particularly threading granularity issues with physics simulation when running large craft such as space stations or complex rocketry. There are some amazing KSP videos on YouTube with orbital construction on a grand scale, gigantic interplanetary vehicles, complex planetary bases and so on; their dirty secret being that the original gameplay is actually occurring at a painfully frustrating <10 fps and has been massively sped up for consumption.
GP is suggesting that using DOTS those issues can be relieved, by making more efficient use of available system resources.
ECS and DOTS aren't quite ready for prime time by Unity's own standards so there aren't many games actually shipping using ECS or DOTs because the API isn't stable.
