Earlier quoted context omitted.
As with all departments in a company, HR does the tasks that they're assigned to do. It's a task, not a mission. There's scope creep and mission creep as with every task we're used to. If they do stuff that they're not supposed to do and make decisions that they're not supposed to make, it's the team and the person handling the team that's broken and time to reevaluate and adjust what value the team is supposed to br…
What, specifically is that task?
The scope can be as narrow as "do background checks on hires, do the math on their desired pay and tell me how much each one would cost and if there's any red flags" or as broad as "do a first phone call and check out if you think that person is a good fit culturally." Handle all associated paperwork, set up interview dates, handle travel and accommodation arrangements for the prospective hire, ... Handle all paperwork associated with employees, sick leave, keep track of holidays, ... Follow changes in applicable law. Organise team building events. I know of an HR department that organises monthly lunches where people of the company get randomly assigned to groups so that they get to know other people working in the same company, not only their team peers. There's a lot of things you can do as HR person. Not everybody needs everything and not every HR person may have the required qualifications for each task, so you probably just have to figure out what exact set of responsibilities right for your place.