I don’t buy it.

It’s not as bad as Gearbox complaining about Unreal (which they’ve worked on since 2005), but all the coverage I’ve seen points to self-infliction.

They’ve worked on Unity since at least 2014.

And other lower budget Unity sim games like Humankind, Timberborn and Ixion (just to name a few) run fine, and look great.

Now, maybe Unity's overhead and issues is a factor, but it’s not the only one. They messed up.