I for one have long since memorised all the keyboard shortcuts for screenshots. And for everything else there’s command-shift-five.
I haven’t personally used clean shot X, but a tool has to be way, way, way better than the built-in default to get me to change. It doesn’t matter what clean shot X can do better; clean shot X loses because se it isn’t going to be on every Mac I sit in front of.
Marking up images, being able to blur out certain areas of an image, OCR, Visual indicator of keys pressed in screen recording mode. Cleanshot is really just a screenshot tool with some minor but useful editing tools.
OCR's built in to macOS these days. Works pretty well. Would have been a notable feature not that long ago, though, true.
Better screen recording would be nice but I do it rarely enough that Quicktime is fine. If I did it more I'd definitely have to find some other solution.
All the marking up and such—well, there are many reasons that Preview is possibly my favorite single program on Macs.