The tweet is part of a conversation about building a database for your business, it has nothing to do with play and experimentation for the sake of learning

It's just a twitter take, overcompressed and lacking nuance. By all means write a toy database for learning purposes, but in 99+% of cases you should probably then turn around and use the ones with tens of thousands of engineering hours poured into their correctness properties when you want to put something into production.

I think it's pretty obvious that they're discouraging the impulse to implement a database for your job, not for just playing around and learning.

The key to making breakthroughs in knowledge - either personal or societally - is to choose your battles to a degree.

There is simply too much to master, it’s a very good skill to be able to say “this is fascinating but too far afield of what I need to do”.

Alternately, choosing when to say “after dipping my toe in the water this clicks for me, I’m going to take a risk and go further” is an even harder skill to master.

This is why many people have trouble finishing a PhD dissertation. Play is a necessary step, but play without focus is a ticket to mediocrity.

Databases in particular are something one will run across in nearly any task and 99:100 times one likely shouldn’t dwell too much on what is inside the magic box.