The way to solve that is "just" to increase the skill ceiling in some other dimension. Warcraft 3 has easier macro mechanics than SC2 - five workers per gold mine, less expands, less unit-producing buildings, wood as a resource is often a non-issue - but makes up for it by having a higher skill-ceiling when it comes to micro mechanics.

You could for example make larvae inject optionally auto-cast, as long you add some other mechanic that the zerg have to (or should) worry about (like more complicated creep spreading, for instance).