This question or variations thereof has been asked (and answered) countless times.
See @joreg’s answer from 11 years ago:
that is because all of vvvv runs in only one thread. while the gui is blocking the mainloop nothing else can be computed. there is no workaround on your side but we’ll have that fixed one fine day.
And @eno reported recently
After a really long day (2 a.m.), looking at our project, trying to understand VL and taking first steps, Sebastian pulled me over to his desk, saying “hey, I’ve got to show you something”. And what I saw was a prototype of v4 running on multiple evaluator processes. I was baffled.
After that, Elias took over and showed me a v4, where the interface was running in a separate thread. Rendering unimpressed by UI interactions.
We talked for a very long time. And for both of the prototypes there are very good reasons, really severe problems, why they are not a reality yet; and probably also never will be
So until the group makes some kind of official statement people will keep asking & guessing. Limbo.