I use Linux on my workstation, Windows at work, and Mac on my laptop. I don't get what's so terrible about the Finder. If anything, it makes you miss column view in other desktop environments (and space to preview!). [An aside, regarding Open/Save file dialogs: dragging a file into an open dialog is great, and neither Windows or Linux have been able to do copy that functionality. The best you can do is to copy and paste a path.]
I've asked this before and I've never received a list of grievances which led me to conclude that people are just not familiar with Finder.
Have you used ranger, Linux's command line visual file manager? You might like it. Navigate directories/files with arrow keys, space to open/view, ton of shortcuts for eg copy/paste/move/rename etc.
You're right that the problem is unfamiliarity rather than a lack of features per se, but since every other GUI file manager 'just works' (I can intuitively tell how to do basic tasks) and finder doesn't I think it's a legitimate complaint.
I've asked this before and I've never received a list of grievances which led me to conclude that people are just not familiar with Finder.