[golergka]

> write their own tools and extensions (e.g. memory management)

I've been using Unity since 2009, and have been a lead developer and CTO in several different companies. I have never heard anyone writing their own memory management for Unity. May be you're talking about object pooling?

[squeaky-clean]

It's kinda what ECS is, depending on how loose you want to get with the term memory management. And studios have implemented their own ECS in Unity long before Unity's official ECS framework.