The GIMP was really hard to use and lacked a lot of features, but the re-did the interface a couple of years ago and it is supposed to be easier, quicker and more professional now.
I worked at a photo studio that thought they would save money and go all open source. It used Open Office for general work and it started using The GIMP for image processing. They quickly backtracked and went back to using Photoshop for the main editing.
I have Photoshop Elements, Affinity Photo and Paint.NET on my machine and I used Photoshop in the past. They all have their strong and weak points. Paint.NET is very basic, but it allows for very quick and dirty image resizing. On one project I worked on, I’d use Photoshop for retouching images, but a lot of work was simple cropping and resizing of existing JPEG images, Paint.NET was a lot quicker and easier for this simple task, even when I couldn’t use it for touching up the images. I could have done all the work in Photoshop, but for a couple of specific tasks, Paint.NET loaded quicker and its interface allowed me to do what I wanted with a couple of clicks, whereas Photoshop took an age to load and the “simple” features were buried on Photoshop - if I had been a Photoshop expert, I might have been able to do the job just as quickly (excluding loading time) in Photoshop.
At the end of the day, it is what you are used to and what exactly you want to accomplish. The GIMP (and other open source, freeware or cheap packages) have their strengths and weaknesses, as does Photoshop. If you are starting out, learning either The GIMP or Photoshop (or any of the other packages) is going to be a steep learning curve, so it probably doesn’t matter which one you choose. If you are going to try and work in the industry (in a studio with others, not as an independent), then Photoshop is probably the better investment in your time.