I agree with all this. I would also add that you should avoid complexity. If you can't explain it to an engineer or you need a lot of arbitrary branching logic

I agree with all this. I would also add that you should avoid complexity. If you can't explain it to an engineer or you need a lot of arbitrary branching logic (the engineer will tell you), its probably not a wise decision. When engineers complain about complexity, it's not because they're lazy, it's because they know complexity is a liability and usually un-intuative in the UX. This is related to adding features as different features may interact with other features or add complexity as to what it is your product actually does. Also something engineers should know: no one cares about your stack. Apply the minimum technology required to perform the task. No customer will go with a product just because it has a particular stack. Make it as simple as possible, but no simpler. Sometimes engineers push over-complicated technologies they are passionate about or want to learn for their own sake. You should be somewhat aware of the technology being proposed and get the input of other engineers when its something that is non-standard.