Absolutely. The number of players involved and the level of information asymmetry mean that it's not even knowable how the market is or isn't irrational.
You're basically arguing that "alpha" is an illusion borne out of the quirks of distributed probability. I (along with many leading minds in finance) also believe this to be true. What many hedge funds call "alpha" is often just dumb luck. In the few cases that it isn't, policy changes at central banks are often involved (this is why it's taken the fed several years to choreograph the wind-down of QE).
But the irony here is that the fact that everyone believes they can beat the market is what makes the market as efficient and liquid as it is. If everyone traded with the same strategy, you'd see massive swings in volatility and information asymmetry would be an even bigger issue than it is. Because there are so many different trading strategies built to hunt out arbitrage in certain pockets, the market as a whole is incredibly efficient - or at least more efficient than it would otherwise be.
Whether or not they are capable of guessing the direction of the markets is irrelevant: if you take a portfolio strategy and make equal bets on enough different assets, you'll end up with something that is probably close to the market rate of return anyway. Note that this only applies to the "professional investor" class (as defined by the SEC); everyone else is simply better off in mutual funds. Professional investors have access to classes of securities with a higher average rate of return than normal citizens do, so they likely can beat the market as long as they're also able to absorb big losses in the years they don't beat the market.
Unfortunately, "the market is irrational" doesn't imply "you can name the ways in which it is irrational" nor does it imply even that there exists any single entity that is capable of correctly naming the way in which it is irrational. It is perfectly capable of having, and indeed almost certainly has, a chaotic, highly-information-packed, very fast-moving irrationality that is beyond any human or human institution's ability to understand, quantify, express, predict, control, harness, or "fix". I do not mean that figuratively or metaphorically... there's no reason to believe the market's irrationality is even remotely comprehensible.
So the argument shouldn't be phrased in terms of whether the market is efficient or not... everybody knows it isn't. So let's cut to the chase... why do you (for generalized values of "you") think you know better, and if you do know better, why aren't you using it to make a killing, or, alternatively, how about you write down some interesting predictions about what's going to happen in three or four years and demonstrate the rightness of your theories? Say something interesting and verifiable, and let's see how you do.
In the meantime, merely making the tedious observation that the market isn't "really" rational gets you no points, and I perceive no obligation on my part to change any of my political beliefs merely because "the market isn't rational". On the other hand, make correct predictions years in advance, especially if you can do so reliably, and I will sit up and take notice, I promise you. But, be warned, I'm very familiar with the process of bending a prediction to fit the data and that's not going to cut it... I demand that you be right, full stop. If you can't do that... welcome to the group of people who know the economy is irrational but can do nothing meaningful about it, population: entire rest of humanity.