VVT, DOD & DI are all technologies that provide additional tuning benefits, but that add complexity expense & failure points to the engine without a benefit significant enough to compensate for it.
As these technologies were added to the LS the engine became less reliable but removing that tech was easy & restored the former benefits to the engine;
if the LT is to ever become a staple like the LS it will be because of the ability to affordably ditch the unreliable aspects & simplify the processes back to a reliable engine that can handle significant performance increases without falling apart.
What works is what works, all the claims about advantages with the more involved technology never matter if the added failure points nullify the benefits.
You can hit & maintain a target AFR consistently with computer controlled port fuel injection, the injectors do not need to be introduced to the combustion chamber & its DESTRUCTIVE environment to achieve a reliable AFR;
it just costs more to develop injectors that will work in a combustion environment & it reduces their lifespan to move them to the combustion chamber.
VVT can expand the optimal rpm range of the cam profile beyond a static ground cam but not without adding cost & reducing reliability to a point that nullifies the benefit,
DOD is just a gimmick to please the EPA that provides no real advantage in exchange for its failure prone design
Not sure if I agree with you on Variable Cam Timing (it varies the cam which varies the valves).
Guess the deciding proof for me would be to take an L92 / L9H, disable the Variable Cam Timing,
custom grind and install a cam meant to meet or exceed ALL the performance targets hit by the GM OE cam with its VCT active,
and if the custom grind 6.2L performs as well or better than the GM OE 6.2L, then I'll agree with you that GM's VCT is worthless.
Direct injection and Cylinder Valve Deactivation, yeah, those features are bugs;
I'm convinced they were designed and installed with the express intent of harming the Gen 5 / LT V8s' durability / reliability at or past 175,000 miles.
Put another way: GMT800s and early GMT900s are hurting GM's bottom line.