RP is always difficult to pull off in Open World PvP games, failing strict GM/Admin intervention to monitor spam killing and such. It's possible, other games have systems in place for it, but Nin doesn't have a foundation for it outside of relying on the goodwill of the players.
Doesn't mean RP cannot exist on the village level. Kages can push for RP at all times during Org events/activity, for example. Village events can be held where RP is mandatory. It happened in the early stages of Ainz' Mizukage term fairly recently. The problem is it relies on players setting up their own incentives.
The Kage funds his own events through Village Banks that they set up rather than any system the game provides. Ranked ninjas are rewarded for their RP missions only if they make the lowbies pay for them, etc. It's high effort, and at the end of the day people are drawn back to the only thing the game makes easily accessible: PvP.
I don't think this is necessarily the Devs fault. It's a feed-back loop. PvP is easy to find and enjoyable, so most people drift to PvP and demand content surrounding PvP, further isolating anything that isn't PvP. If changes to RP missions were pushed before the current balance patches, for example, people would be losing it.
Any RP is going to have to live with that in mind. Assume the lore setting is a land in perpetual war, where no one is safe, and groups of Ninja have to band together to survive. Maintain RP within your group and when you're inevitably jumped, write it off as an IC attack by hostile ninja.
It limits the scale of your RP interactions but as it stands large scale RP events simply cannot run without a Kage/leadership willing to push for it. The future for RP in Nin is expanding on the village systems, clans, RP missions, integrate village politics and banks. This will make having localized RP easier and more prevalent. Outside of the village, less can be done. I'd especially oppose anything that got in the way of the Open World PvP.