Interesting how systems engineering has two different definitions. We have the one being talked about it, and the 'traditional' definition. See https://en.wikipedia.org/wiki/Systems_engineering. NASA even has a Systems Engineering Handbook: https://www.nasa.gov/seh/index.html

In short, 'systems engineering' as an engineering discipline has nothing to do with managing systems, servers, and networks.

Right, in my experience you’ll run into ‘systems engineers’ in all fields, some are working on interfaces of the systems in that field, and others are thinking of the totality of the system and it’s maintainability, efficiency, and design. You always have to ask a follow up when someone says they’re a systems engineer.

I'll generally start with defining the "INCOSE" kind or the "MCSE" kind and most of the time people from one group or the other will know of the one they are close to and little to nothing about the other one.

the work I do as an ordinary [IT] systems engineer seems to fit that traditional definition just fine, with the work involving systems thinking about, and dealing with, how different parts of company systems interact (different groups' applications, network, service providers, customers, employees, each logical layer of each stack the software runs on, to varying degrees, down to bare metal, etc)

In computing, "systems" are inside and between the computers.

Outside computing, "systems" include non-computer entities.