Can you elaborate on the kind of "serious work" you are doing which cannot be accomplished with one of those solutions?
Obviously those are all readers, so they are not able to edit PDFs or create them from scratch. However, neither can Adobe Acrobat Reader or most free PDF bloatware.
The main purpose is trying to fill out annoying legal / banking forms that have tons of fields and sometimes field validation, digital 'eSignatures', etc. And every browser renderer treats these things differently and often breaks.
Try and work off a 1600 page reference manual for actual work on a desktop. Bonus modern design is informed by the need to support monkey's fat fingering stuff on their smartphone. Any use case outside of that is less and less supported.
Adding and saving annotations/notes/highlights, fast full text search (aggressive preload), double page/single page views, form filling and saving (perhaps not even to the original PDF) are the minimum you really need for "working" with PDF...just "viewing" them is not really enough for serious academic work/research on PDF files. The more well integrated, the better. The functionality should look like in Acrobat, Okular, Mendeley, or similar tools.
Obviously those are all readers, so they are not able to edit PDFs or create them from scratch. However, neither can Adobe Acrobat Reader or most free PDF bloatware.