If by "compromised already at step zero" you mean "just the way computers worked for decades prior to secure boot", then yeah, I suppose.
The issue that I have heard people bring up is that it could potentially make it harder to install free and open source operating systems and thus turn consumer-grade and relatively cheap computers into less of a tool that you can use the way you want and more into an appliance.
For all the panic that ensued when stuff like secure boot and similar were first announced, and the fact that I still seem able to install my Linux distro of choice, I as somebody who has not gotten personally invested in this am not in a position to know how real such an issue is.
But I would like to know what proponents of secure boot think the technology solves and why what we had before inadequately addressed security needs. Because it seems to me that e.g. Windows will still happily get infected with viruses such that whether the boot process itself has been compromised, or just what comes immediately thereafter, does not matter too much. Or does it?