Furthermore, there would be no vulnerabilities if you just unplug your computer and walk away, at some point you need to make usability and risk compromises.
Furthermore, the UNIX user model and file system hierarchy already provides you with RBAC. Combine that with ACLs and SetUID (et al) bits and you’ve already got sudo baked into the core system.
Your point about it being a convenience tool is bang on: it makes it easier to administer all of the above but that convenience, like nearly all convenience tools in computing, comes with a slight security trade off.
To be clear, I don’t agree with the author’s recommendation to ditch sudo. But they are absolutely correct in the technical sense. Just as you are. In fact you are both basically arguing the same point but from different perspectives: “sudo adds a vector of attack”. It’s then up to your threat modelling to decide if that is appropriate or not.
But to come back to my original point: just don’t give people shell access. There’s no need in 99% of cases of servers these days and if we are talking about local user machines, then RBAC is less of an issue since it would be a machine per user.
Also since we're talking about running as root: ironically I've found a lot of people seem to put the following line in their sudoers file:
ALL=(ALL) NOPASSWD:ALL