The difference between a 10% agent and a 30-60% subcontractor is what's being purchased, and from whom. Actors and other famous creatives are selling their particular work, which is unique and demanded by clients mostly independently of details like who their agent is. When a client pays 2x to an agency that pays the subcontractor implementing the work 1x to complete it, what's being purchased is the agency's work - working directly with the client, finding developers to complete the work, and managing the process of delivery (and all the related bits: making sure their subcontractors know what they're doing and are appropriate fits for the project, keeping work on track, being accountable for delivery/operational execution to the client).

If that extra 20-50% were so easy/useless that it can be grabbed "without lifting a finger", why aren't you finding enough work on your own to keep yourself busy, or, why are you still working with that third-party company to begin with? Oh, you would, if you "had any interest" in doing that. That level of accountability to the client and attention to their needs is literally what clients are paying the agency for, and why they're the ones handling the demand for work rather than their subcontractors.

If clients aren't seeking out your particular involvement in their project, you're the guy working the mic, not the movie star.