I love the last paragraph :) for it to become mainstream it must not be rocket science anymore.
As first mover, much money can be made, but with high risk as well.
Providing liquidity to one of the more reliable protocols might be a relatively safe way to earn some interest in your holdings, although when liquidity gets bigger and more stable, fees will become lower.
Since there are now also projects that automatically search for the highest yields, eventually all will get more balanced and interest will be lower. Except for the new risky protocols, until they die or become balanced.