It is all wrong.
People have grown used to dismissing immediate surroundings.
So things are said without admitting they are being said.
Calculating chances is just another term for decision making process.
In this kind of products, the benchmark used to evaluate the quality of decisions is unreliable. Prediction of outcomes is unreliable etc
You call it unreliable, but I call it rolling dice, ie. what an RPG is about. How can you have a combat system or any sort of meaningful system if certain things aren't left to chance sometimes? It would be pretty boring if attacks never missed, crits never landed and so on.
It is about building the highest percentage. When it is relevant. The list is full of examples that are not decided over probability.
Actually it's not, and I gave you examples. RNG in Lords of Xulima supplements the decision-making process by giving you more information and options to consider. Do I do an attack that has a higher chance of landing but does less damage? Or take a larger risk with a power/stun attack that might not hit but if it does we could get an extra attack or two in before the enemy attacks again? They give you options and there are consequences to every combat decision.
When two options are offered: one is an attack the enemy is immune to, the other is an attack inflicting critical damage, the decision is not made over chances.
No matter the chances, the player is invited to decide for the critical damage attack.
A 10 per cent critical attack is valued by design more than a 100% immune attack.
This is a meaningless example. Who would ever attack an enemy with a 100% immune attack if they knew it would be immune? That is not what these systems are about. You often get different risk/reward micro-decisions to make from turn to turn. So in my previous example, you could swing for the fences and take a slightly less chance to hit, or play it safe and take the normal attack, or try something that is perhaps even riskier. But there are options and many different ways the battle can play out based on your decisions + effect of the RNG in a game like this. It's like a GPS that recalculates the destination every combat turn based on what you choose. This makes the battle much more dynamic and fluid as it goes on, while adding more unpredictability, thinking on your feet and having surprises happen (with instances that can either be beneficial or detrimental to the player).
Now quite often, this kind of products introduces valorization by percentage of chances. This is when building up percentage is relevant.
Often, there are ways to increase the chances of a critical attack (buff, position etc) A basic 60% critical damage attack might be turned into 70, 80, 95 %.
That is when failures are destructive.
Nothing in an RNG is destructive. It is psychologically destructive, maybe. 
Of course there are psychological issues and not forcefully tied to RNG.
In this kind of products, the player is led to believed than options can be superior one to another, that there are better ways to achieve than others, to face repeatedly that actually, the difference in superiority is not there.
Players applying inferior (by design) options might succeed more than players applying superior options.
Actually no, not at all, completely the opposite in fact. The point is not that one option is clearly superior or inferior, it's about how you use the various options. Which attacks/strategies you use. The risk/reward factor of each move. If a player is led to believe that an option is superior in all cases then the system is not a good one. The player should be making choices as to which way is best to proceed, and in a good RNG system like Lords of Xulima, that's exactly how it works. You are more often than not greatly rewarded for good decisions, paying attention and thinking strategically and even "out of the box" thinking can work well in the game.
By design, players are called to calculate chances to discover calculating chances is meaningless.
