Alternatives to RCU?

RCU is being used because it allows software to avoid using them and still be correct.

Everywhere that RCU is being used or considered previously used Atomic instructions and locks, and it's being used because it's so much faster.

this is a case where doing things the 'simple' way limits it's performance, RCU looks at the problem a different way and comes at the problem sideways to get the desired result with much better performance, but unfortunantly at the cost of complexity.

RCU actually takes very little run time, it takes a lot of RAM to hold all the extra copies of the data (and all the complexity boils down to figuring out when these extra copies aren't needed any longer)