what features were removed?
i think the only real one to go (AFAIK) was what motorola call dual capacity Direct Mode. What other manuafacturers call TDMA. Hytera still has its Pseudo trunk (which personally is more useful to me). One carves a frequency into two standalone channels, one puts twice the calls on one logical channel. There were some other bits that were oddly remove and not related to Motorola (like abiltity to un-mute the squelch on an analogue channel, which is clearly not patented and is back on the HP series).
I do note that there are lots of smaller manufacturers still including the DCDM, but I guess there is no money in motorola chasing them, and no loss of revenue (no (commercial) potential Motorola customer would buy a ham radio like anytone, Baofeng etc)
I believe there were also some minor audio EQ functions that came out of the PD series but nothing of note from my perspective.
As others say, there is no way back from V9.