The Engineering Challenge of Building Reliable Analog Oscillators

There's an old electronics joke that if you want to build an oscillator, you should try building an amplifier.

One of the fundamental criteria for oscillation is the presence of signal gain; without it, any oscillation is bound to decay, just like a swing that's no longer being pushed must eventually come to a stop.

In reality, circuits with gain can occasionally oscillate by accident, but it's rather difficult to build a good analog oscillator from scratch.

The most common category of oscillators you can find on the internet are circuits that don't work reliably.