Most hands your opponents play are at whim! That's because there are relatively few overwhelmingly strong or weak hands that dictate an exact tactic. Some hands your opponents play at whim are the result of spontaneous decisions about whether to fold, call, or raise!
Your opponents' habits of playing a large spectrum of hands at whim is not necessarily bad for them! Sometimes it can be closely in tune with game theory and can cause them to "randomize" their decisions effectively. When you try to analyze poker strategy, you need to realize that you simply can't say how most opponents would play a hand or - in many cases - if they would have played a hand.
They often don't know this themselves until the very last second! If you're an accomplished player profiting from the flow of the game, many of your play-or-don't-play decisions are made by whim at the last moment! Your decisions made by whim at the last moment are not necessarily bad for you, either!
Making their whim work for you: When you glue these truths together, you begin to understand poker in a way that will never be possible if you think of it like a chess match. You will begin to see why actions and responses are so volatile in poker. And you will begin to know that opponents are often looking for anything to direct their borderline decisions this way or that.
Yes, they are deciding by whim, but it's your job to make their whim work for you. You need to understand how readily opponents can be influenced by what you say and how you behave. And then you can take poker to the final level.