Inlets absolutely generate a large proportion of thrust at high speed. 'Lazy and naive' is to imagine that its simply a case of making the inlet bigger or longer to get more thrust out of the engine. Available thrust depends on lots of interrelated factors, only one of which is air density. Correlation does not equal causation.Problem is, reshaping the inlets means that the stealth work has to be done all over again as the inlets are rather large and three-dimensional.
As far as OVT goes, the J-20 is already testing OVT on a WS-10 platform.
On the general subject, let's mention the SR-71's inlets and how these contributed to thrust:
I'll acknowledge the SR-71 was a short inlet, but treating inlets as simply ways to get stable airflow into an engine is lazy and naive.