> Always write the simplest thing you can, but no simpler.

I don't think so. Time and time again the client will insist on stuff like "the customer only needs a single email address/phone number" but you're going to pay for that one later if you do the simple thing and add an "email" column.

Same for addresses.

And a whole bunch of other stuff...you need to normalize the heck out of your DB early on, even if you don't need it now. The code you can mostly make a mess of, just choose a good tech stack.