A really good question, and evidence that you are quite perceptive. If you read all that I have written on the topic, you might think that I contradict myself on the question of irreducible complexity. I cannot blame you one bit for being curious what is going on. Well, here is what is going on.
The reason what I have said can be confusing is that I believe some irreducible complexity arguments are valid, others are not valid and still others are debatable. Let me be clear. It has been the practice of many intelligent design proponents to come across highly skeptical of the overall theory of evolution. They have argued that microevolution happens but macroevolution has not. They have used irreducible complexity arguments, for example, to say that the human eye could not evolve from simpler systems. This argument for irreducible complexity in the vision proteins is sometimes called a gap argument. These gap arguments are questionable at best. In fact, it is my personal opinion that in many cases they are simply, verifiably wrong. Specifically in the case of the evolution of the complex eyes of mammals, every single step in the formation of the complex proteins that allow for vision has been shown to be a reasonable sub-step which has other possible uses. Here is the bottom line. Gap arguments against evolution are not generally convincing. They are subject to being either disproved or shown to be unnecessary.
It is my personal belief that a fully random process is not sufficient to explain bacteria-to-human evolution. It is my personal belief that God has intervened in the course of evolution. In particular, I would point to the Cambrian Explosion, but also to the vast chasm of successful mutations needed to cross from single-celled life to advanced life forms. However, I am hesitant to form this into a specific irreducible complexity argument, and I tend to argue theologically as much as or more than scientifically in my skepticism about fully random bacteria-to-humans. I do not use irreducible complexity arguments there. I explain this hybrid theological/scientific approach to evolution in an essay Four Christian Views of Evolution: https://evidenceforchristianity.org/four-christian-views-of-evolution/
But… I believe that there is a slam-dunk irreducible complexity argument. And here is where the confusion can come in. I believe that there is an uncrossable chasm of irreducible complexity between non-life and life. A living system has a vast quantity of pre-existing information which can be used by the God-created process of evolution to create new kinds of information. Science tells us that. However, science also tells us that random processes do not produce information where there was not previously any information. The complexity of the simplest living thing is enormous. To go from literally almost zero complexity/information to the hundreds of millions of pieces of information required to sustain a living thing is a gap of irreducible complexity. The in-between states cannot self-reproduce. This is completely different, for example, from the case with the evolution of the eye. Each of the in-between steps (some of which have not yet been demonstrated yet, by the way, but that is beside the point) involve a viable living thing. It is possible for there to be one million and one steps forward and one million steps back. The net result is one step forward. Non-living systems simply do not do this. If there were to be a theoretical step forward, such a step would immediately be undone by the process of natural entropy increase, as the newly-acquired piece of information cannot be reproduced. There are no exceptions to this law. The second law of thermodynamics does not allow for the increase of information where there is none.
In summary, when it comes to critiquing the theory of evolution using arguments of irreducible complexity, I find such gap arguments to be weak at best and subject to being either disproved or at least undermined by science. However, when it comes to the creation of life from non-life, otherwise known as abiogenesis, I believe that irreducible complexity is a drop-dead overwhelmingly strong argument. The best book I have read so far on this is, ironically, written by an intelligent design person. It is Signature in the Cell by Meyer.
This is why my statements about irreducible complexity can be confusing to readers. I suppose I should make this more clear. Actually, I just did! I hope this helps.