Not only is it resource‑intensive, but Qubes also lacks Secure Boot and Wayland support. Secure Boot is critical to ensure the OS has not been tampered with, and Wayland is required to isolate individual apps running within a single VM from capturing input intended for other apps. For an average user, I would recommend SecureBlue rather than Qubes.
Proton is targetting enterprise who would love a secure alternative to Google Workspace. A normal consumer don’t need to put all eggs in one basket. I don’t think Proton is forcing you either. I just use their paid email service.