The problem is not in the 51% vs 49% chances of a success but in how people underestimate the power of a streak of luck and unluckiness. That is why some people get 6 or more streak of fails and some even reach +40 or more with only a minimal loss in their potential.
There’s a good video explaining how Streak works.
I am in no way defending IMC. I also want to upgrade my gears and turn them into shiny without the fear of destroying them or rendering them useless… They really opt to streamline this mechanic like how they did transcendence where people pay more to increase the likelihood of a success they also need to cap their upgrade levels to a minimum so everyone has a somewhat fair advantage overall specially on pvp and gvg scenario.