Proper project scoping (or to rephrase: identifying the true core business needs) is truly one of the hardest problems in tech. Over-scoping makes you end up with a ponderous system that doesn't serve core business needs very well, while underscoping can lock you into poor initial decisions that cripple your ability to expand into other related functionality.

What's the expression? "Plan your system for 100x growth, but build your system for 10x growth". Something like that except for functionality rather than scalability.

That and supporting the system. Junior engineers tend to think about building the tech, which is honestly the easy part. Keeping it working until the last of your customers are finally ready to upgrade 10 years later is harder than junior engineers tend to think.

Ha!even this sounds like a mistake to me. How about "Make the simplest thing work for one person.". Make sure they get some value, and then iterate and repeat. Once you've clearly solved the problem at hand then start to scale, optimise etc That is of course all after you've presold the solution.

I know it's not always easy to do this, but that really is part of the challenge. There's still too many deathmarch projects lead by people trying to do things 'the right way'. If you're working on a new project for the love of science, please make sure you're releasing something valuable every single week if not every one or two days!