Cool Down needs to be made rare in this game

No.

Actually, every champion getting some CdR from itemization is good for the game - it makes balancing work a lot easier. Cooldowns that are appropriately long in lane can be way too long in the later stages of the game, and vice versa. Also, CdR being readily available means that balancing can be done with that in mind, and they don't need to worry about champions that are being balanced around no/low access to CdR finding a build that gives them access to capped CdR without gimping them and breaking the game in half.