SW is weird in that way, we can basically build houses that nobody wants to live in. Thing is you probably were building the right thing, structurally speaking.

My rule over time has become "structure follows complexity" i.e. Anticipate complexity where possible but don't apply the engineering structure until the complexity really exists. If you built an MVP house, don't add the second bathroom until you've got customers complaining about deadlocks on the first.

It's tough because that basically runs counter to the Spirit of an Engineer, which is just to imagine the grandest well-thought-out + organized thing and march toward creating it.

The bonus of having two decades+ in building SW though is you start to see the patterns and realize that the same fundamental needs drive everything, so the intersection of building something great with customer needs becomes less of a mystery and more of a "how fast can we juice this thing". At that point I think scalability prep is like compound interest.