I went from a TH-57B to a TH-57C to a HH-65A, which had a starflex rotor that turned the other direction, a fenestron, real AFCS, crude FMS, Marconi gauges, and a wee bit of primitive monochrome glassy stuff. Other than being appallingly underpowered, it had little in common with the TH-57.
Yes, one does adapt, but the learning curve was fairly steep, as it was for my contemporaries going into Sikorsky products. It's steeper now.
The jump from a clapped-out TH-57C directly to a 60 variant or a new H-1 is fairly huge.
Sims I suspect and hope will be a big part of any new training procurement. I need to jaw with the sim boss at exciting Whiting. He owes me a beer anyway.
AAKEE makes a good point about the possibility of an easy-to-fly modern machine masking weak handling skills. I would think that will be a real issue. So too may be a loss in the ability to fly raw data from needles and DME unless it is explicitly taught, which remains a necessary skill set for lots of stuff, such as SAR and mucking about with TACANs, if such crude devices still be used.