Rust dev is bored of paying Unity '$500k a year' to fix its engine and promises that his Garry's Mod successor won't hoodwink devs with fees

First he tells Unity to piss off, then he literally says "Unity has been good to us." He is complaining that he pays his staff to optimize the Unity engine, but has he already optimized his own game first? Seems like the classic fallback of a developer when their game has bad performance: just blame the engine rather than their own code.

He really thinks he can spin his own engine that will be better than Unity/Unreal/whatever, does he know how long it takes to develop a good, performant engine with the features necessary for what he is trying to make? Even Unreal, which has been around since like, the late 1990s, has difficulty with optimization and performance. He thinks he can do better? More power to him, I guess. Let's see if he can.

Garry isn’t even technically building an engine from scratch, right? I thought S&box is heavily modified Source 2.