I'm curious how this works in practice. It's been several years since I used an automated job application system, but I remember they would usually parse your resume into a limited set of form fields that you then had to manually check and submit. Are modern systems used by desirable companies really as simple as upload your resume PDF and off you go?

Yup. I did this a few years back after getting frustrated with few responses. After doing just that they increased significantly. People will say it's not worth it, that it doesn't work in general or because "companies are updating their systems", but from my experience it totally is worth it and apparently a lot of places still aren't using solutions that vet this.

Worked particularly well with getting responses from gov applications lol