If we take oppression to mean unfair or unjust treatment of people over a sustained period of time, then why does it not apply? The fact that institutionalised societal disadvantagement may exist in much milder forms than slavery and voting disenfranchisement doesn't mean it isn't long-term unfair and unjust treatment.
I disagree that an individual person showing favouritism to other individual persons is "oppression." It's a shitty thing to do, sure, but not "oppression."
If the sum of your argument is merely to protest semantics becuase you think a term is a bit harsh (especially when that word has been widely used in that context for many years), I'd suggest you're not arguing something interesting and important.
No, it's not.
I mean, I'll make it perfectly clear, if people start calling me/thinking of me as an "oppressor," I've been called/regarded as far worse on these forums, "oppressor" is quite mild. But if you're subscribing to a belief system that labels people into oppressed, oppressor, or both, then, well, can't say it's an idea I agree with. It trivializes actual oppression, and it's a very blinked way of seeing the world.
The second issue is this idea of "oppressor". You are right, that receiving benefits does not necessarily make one an "oppressor" (not least because it would be the person who is deciding the allocation of resources that would be the oppressor, not a recipient of unfair gains.) But more importantly, the "oppressor" is not usually personalised in this situation, the oppressor is better seen as the general system or society, where many of its beneficiaries have neither intent nor even awareness of their advantages.
Well, I think saying "the system" is a cop-out. By the job example, it's not "the system" that's being a dick, it's the manager. Or, if you want to point to an actual system that's codified preferential and/or discriminatory treatment, then sure, the system is at fault, but it's still individuals who designed the system. Granted, I think that does provide an 'out' for some people (the "following orders" defence), but if your entire paradigm for looking at it is oppressed/oppressor, then it removes any nuance, assumes guilt by association, etc. I mean, if someone gets hired for a job, and finds out years later that they only got the job because a family member pulled strings at the company, then however that person might feel, it's silly to say they're "oppressing" anyone.
Like, to give an example we've both been on the Ukraine thread, we both know how Putin's levelled the charge of Nazism against an entire country/government, based on the real presence of actual Nazis. If one's going to level such charges, then it best be used accurately, otherwise the term loses all meaning. Or, to use another example, North Korea. NK's probably the most oppressive country on Earth (and yes, I do believe that statement), that doesn't mean I think every citizen of North Korean is an "oppressor," it's the regime. Guilt by association isn't a good way to see the world IMO.