A lot of these girls I used to follow became the other way around. yungfreckz, tally, cassie, samlily, lovelylilith, courteousraspeberry.
They get comfortable doing the bare minimum because they still get paid. they have a "stable" foundation of people subbing so the money keeps coming in. Ninapai is no exception here. Very few girls actually keep innovating or trying.
I'll also say Nina seems to do something shady, which is, the best TFs she records, she locks behind the $150 paywall. You can tell these are always a bit better, be it in outfit, or angle, or overall movement. Don't care much about the vids where she has the other girl as she barely does anything.