Thanks for sharing your feedback! I've just sent you an email with a couple of additional questions about your expectations from the app.
It looks like the website works in Safari on the iPad. Maybe that's enough? Aside from offline access/editing.
+ 1 on IPad app, it's really needed
Is it best practice to use the RTB app or a browser on iPad pro with pencil? And for the app do you need beta testing and/or specific types of feedback?
I am very surprised that iPad Pro + Apple Pencil support is not supported, especially since you already have an iOS app.
Whiteboard collaboration with a distributed team without fluid high quality stylus support neglects an enormous market.
Whiteboarding with a mouse and keyboard (no matter how many optimizations and keyboard shortcuts you use) is not as fluid or natural as a stylus. The software gets in the way of expressing thoughts and ideas.
I am currently evaluating whiteboard software, and this is a make or break feature for me and my team (20+ team members in 3 timezones).
You would have a killer app if you added iPad + Pencil support. Without it, I must look elsewhere.