First-gen here. I want to echo this. Also, do not forget that some professors - undoubtedly some on the adcom - are first-gens themselves.
I see many posters writing authoritatively about what will be the most crucial element(s) of the application or what makes a stellar application. Based on what? Second-hand anecdotal evidence? A "logical" deduction of scattered and unverified information across Gradcafe and Reddit? Your intuition? A professor once told you?
While it is true that SOP's, WS's, LOR's and grades all matter in some way, I think it is important to emphasize that adcom members have some agency and aren't just ticking off boxes like robots. One of the reasons why we are all waiting for such a long time is because picking out the right candidates requires considerable deliberation based on the sum of variables that constitute your application.
As _baby__yoda said, there are many cues that can signal graduate school success. The combination of those cues will be unique for every candidate. Maybe your GPA is low, but you have 4 competitive scholarships. Maybe you have only taken two quant classes in undergrad, but you worked as a data scientist for 3 years. Maybe your background is not in political science, but you published in a top political science journal.
And then, say if you have made it into the "promising applicants pool," much will come down to luck (an element we routinely underestimate in daily life) -- it is truly a crapshoot.
Rooting for all of you.