Re: "especially in the startup markets"
"It's this attitude that keeps Linux away from many desktops, and I'd really like to see more alternatives - even non free ones - to Windows and macOS applications"
I do understand where you're coming from. For me, I use Corel Aftershot Pro, Pixeluvo, Polarr and Photomatix for photos on Linux (I quite like Pixlr too) and I don't have to go anywhere near GIMP (the 2.10 version does appear to be a significant and upgrade and improvement though). I know of other photographers who are successfully using versions of Photoshop and Photoshop Elements via Wine and it is possible to use Adobe CC apps online too (look up This Script Helps Install Adobe Creative Cloud on Linux).