An option to link accounts could help with one aspect, i.e. updating balances as they change over time... but I get the sense that it's a can of worms, and it seems like the larger incumbents that do that often have syncing issues anyway.

But beyond balance updates, it seems hard to avoid having a ton of input fields in an app where you build a detailed model of your future. It feels like there's a tradeoff between being able to build a super detailed model and having a comparatively frictionless experience where you don't need to enter much.