I'm no expert but if most single developers only use 5-10% of the codebase in their daily life, wouldn't it make to maybe break the project into multiple codeba

I'm no expert but if most single developers only use 5-10% of the codebase in their daily life, wouldn't it make to maybe break the project into multiple codebases of about 5% each and use a build pipeline that combines them together when needed? Although I could definitely be wrong but this sounds a lot like monolith vs microservices to me.