I did mods on mine simply because it's so easy to add things to make it look better, or in some cases make it easier to work with. I think the only significant improvements for printing were adding an arm to change the angle of the filament entering the extruder, and a fang duct which helped a lot with bridging and stringing.

I didn't really do anything major until I wanted to print with NinjaFlex TPU so I printed and assembled a direct drive head, compiled a new version of Marlin to move the motors the right way, and included some extra features that help print more consistent lines. Yeah that's going to be way outside the comfort zone for most people, but my printer always worked reliably for the three years before this change (I got it at the end of January 2019). I've been working on other projects this year so it's been awhile since I printed anything, but I know I could clean the dust off the bed, load up some filament, and kick out a print job. It just works.