Critical strike chance is not a broken stat. Let me explain
Simply put critical strike chance is a stat that gives the user a chance to UNRELIABLY deal double damage
That previous sentence states everything that is right and wrong with crit in League of Legends, however critical hit chance as a stat is not broken. A stat that allows players to spend their gold for a chance to deal more damage on basic attacks and corresponding abilities but otherwise does literally nothing else is a healthy risk that a lot of our favorite games enjoy adding to their otherwise different game mechanics. The catch however is making sure that the actual reward for taking the risk, in combination to its accessibility, is not so great that it becomes overbearing and over-tuned. Let me explain.
One of my favorite game series has to be Pokemon and most gamers are familiar with basic Pokemon mechanics. Pokemon is similar to League of Legends with comparable stat categories and also has in the past implemented the double damage critical hits in it's own damage formulas. Now allow me to ask your childhood a question: Have you ever lost a battle to a lucky crit before? If you have EVER felt that feel you can understand why Pokemon has since reduced the amount of damages dealt by critical hits to a 1.33 multiplier instead of the standard 2.0. Although initial accessibility to critical hit chance is pretty high in Pokemon compared to LoL (basically almost every damaging attack) , critical hits were previously so game changing this forced Pokemon game designers to limit the accessibility of additional critical hit chance by keeping the efficiency of items and moves that boosted critical hit chance to a severely weakened state for multiple game generations. Reducing the multiplier allowed the Pokemon game designers to increase the accessibility of critical hit chance, retain a healthy amount of RNG in battles, and in general allow investing in critical hit chance to be a healthy and viable option in the ever diverse Pokemon competitive battling meta.
I understand that League of Legends is NOT Pokemon but I do believe that LoL also suffers from an overturned critical hit stat. This is most evident in the continued stagnation of the Attack Damage Carry aka Marksman role's build path. Historically, the marksman build path has been the least diverse and most attempts to diversify the role's build paths are over shadowed by the pure damage awarded by critical strikes to the point that role is arguably balanced around it. The build path has been motivated by simply "what is the most efficient/effective combination of damage and critical chance in the game for X champion?" instead of " What can I buy for my champion that will allow him to be more effective for this match-up?". ADC's rarely ever consider their enemies when considering a build path due to the pure damage afforded by critical strikes typically being the smartest go to option regardless of the enemy team composition. This thinking effectively shows why ADCs have been slowest to adapt to the current Tank meta- which currently directly counters their default build path.
TL;DR lowering critical strike chance's bonus damage will allow for easier balancing in addition to opening up more diverse build paths for ADC's
That's my lunch break guys. Leave comments and questions below