Using iPhone 8 Plus, latest version of iOS 12, and I've been having this issue since Day 1. If anything it's gotten worse. It used to be that the app would freeze up for a minute or two and then I could create a project (and then things would freeze up again after a little bit). Just updated to 1.0.3, and the app is STILL freezing after loading up the project list, and now it never unfreezes. I don't know what bugs the latest update was supposed to fix, but it hasn't done anything for my install. Uninstall and reinstall does nothing. For the record, I have a lot of fonts synced via Adobe Fonts (don't know how many exactly but it's in the hundreds for sure), but I told that to the last support person I talked to, and that was in OCTOBER. Are you guys any closer to resolving this, because I really don't want to have to pay for the features in another mobile video app, only for this to be fixed soon thereafter, especially when I'm already paying nearly $60/month for a CC subscription.
So sorry for the delay! I believe the fonts could have a huge impact on Rush, but I wouldn't expect that they would make the app unusable. I wonder what would happen if you turned your cloud sync off for a project?
So I went and talked with the Rush team about this and they said that having a lot of fonts can affect the performance of Rush. It's being investigated but software development can pull tricks on you. Of course the goal is to have a fix out ASAP!
I know it's inconvenient, but I'd suggest uninstalling as many fonts as you can before using Rush.