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Designing reliable and flexible software systems is tricky. While it's relatively easy to sketch a solution for the rosy scenario, finding a solution flexible enough to handle corner cases without losing integrity is very hard. Adding more abstractions to the design can make life a lot harder for your users, whose experience can turn out less intuitive than it should be.
Conflicting forces can easily lead to a stalemate during collaborative design sessions. It's already difficult to achieve simplicity and flexibility together, but reaching them simultaneously is almost impossible.
Unfortunately, it may be necessary. Not every software project is an MVP, and not every company is a startup. We might need to find precisely the best trade-off between flexibility and simplicity.
You may want to combine the simplicity of Rush to the goal with a different style, after you have delivered a good enough model for the baseline scenario. Start injecting complexity and variations, or pick the ones you deferred in Hot Spots and refine your model accordingly. If your model still holds, you can keep raising the bar to include tricky corner cases, to assess their impact on your current model.
Keep an eye on the user experience by ensuring the perceived value at every step isn't affected by the changes you apply. You might have to balance flexibility with simplicity, sometimes keeping the complexity behind the scenes.