How have production techniques changed over the years?
This is potentially a HUGE question and it would take an entire PHD thesis to answer it fully.
However there is an amazingly short simple answer too...
Music production techniques always change to use the latest available technology.
And not only music production techniques, but composition and performance techniques too.
For instance, a long long time ago there was no such instrument as the piano. Composers and performers used harpsichords, clavichords and organs.
Then Bartolomeo Christofori invented the piano, which is a very much more expressive instrument. Suddenly composers wanted to write for it and performers wanted to play it.
So coming back to production techniques, compression and equalization were invented to solve problems with early technology. But in the 1960s, engineers and producers realized they could do wacky creative things with them. And so they did. When the pan control was invented, producers went crazy with pan effects.
When the electric guitar was invented, the world went electric guitar crazy.
When the synthesizer was invented, the world went synth crazy.
When the sampler was invented, the world went sampler crazy.
When the sequencer was invented, the world went sequencer crazy.
As you can see therefore, the usual pattern is for a technology to be invented, then creative people will use it to death.
Then there will typically be a lull period when the audience is bored with each once-new effect. (Untypically the piano never lost its popularity, the electric guitar however had a lull period during the 1980s.)
But after a while, some enterprising producer will want to go back to the sounds of an earlier era, and a new generation of buyers will be eager to hear sounds they were too young to have noticed first time around.
So, some advice if you want to keep up with musical trends...
When a technology is new, you should jump on the bandwagon quickly and exploit it to death. When people tire of it, look for the next new technology.
But whatever you do, don't be late. There's nothing worse than arriving at the party when everyone is going home.