I'm sure it's possible to get good rice out of an Instant Pot, but the Zojirushi is going to simply be better at it, and it doesn't really take any "dialing in" to get there; you just set the kind of rice and go pretty much, and then you get basically exactly what you want, every single time. Another advantage to a dedicated rice cooker versus using something like an Instant Pot is the obvious fact that it frees up your Instant Pot.

(Also, obviously, there are cheaper rice cookers than the Zojirushi, but there's definitely a reason other than cargo-culting why it's popular. I got one after the Walmart Made-in-China special I got crapped out on me. It is definitely, by a good margin, a better product with thoughtful design that produces very good rice.)

No. We got rid of our rice cookers and replaced them with Instant Pots. Instant Pots make consistently good white and brown rice, faster.

Is there a point to getting a rice cooker over a pan of boiling water?

Absolutely, I've yet to see good rice from an instant pot. Buy the cheapest rice cooker instead (usually like ten bucks).

They're different appliances, no?

The rice cooker cooks at atmospheric pressure, and stops cooking when all the water is evaporated.

The instant pot is a pressure cooker.

In the end, it depends on your use case. If you cook a lot of rice, you will be disappointed with the instant pot. In my case, I don't have a rice cooker b/c I don't cook rice very often, and I use my instant pot or the stove top.

Only if you cook rice like, every day, or multiple times per week.