You need several different apps to do the same as Irfanview.
Why would I want an all in one? Wouldn't I want ones that are the best at what they do, but can hand off functionality to other programs if they excel at it? I just don't find the case for it compelling at all. From any viewer in linux I can launch others applications or have complex workflows.
As for ShareX: Spectacle (default in KDE) covers the capture end (snips, ocr, edit, etc), and then of course uploading is simple enough with various tools. Automation is easy.
Although I gotta give ShareX some love. I used to use it at work, it was great at the time. Being open source made it even better.