Problems arise when people reach for the Cool Tools and start building Webscale things that can handle 100M operations every second. ...but the customer only needs the system to handle 4 users who type in everything crap by hand. But hey, it has a clustered database and Kafka and Kubernetes and looks REALLY good on your Resumé.
When the scale is determined, I personally like the mantra of "Make it work first, then make it pretty". First build an MVP (or an ugly Viable Product), that proves your plan actually works, then you can iterate over it to make the implementation cleaner or faster or have better UX.
If you get stuck making everything super-generic and able to handle all possible cases, you'll spend time bikeshedding and never get anything deployed. Just Repeat Yourself with wild abandon and copy/paste stuff all over until your Gizmo actually works. You can spend time figuring out which parts are actually possible to make generic later.