Some professionals shoot to JPEG and hand over their files without looking at them. Some shoot to JPEG and use Photo Mechanic to sort their files, only handing over the top so many, based on contractual obligation. Some shoot to raw files and use Photo Mechanic to sort and convert before handing over their selection. Some swear Lightroom is the only tool they need. Some use Photoshop. Some use GIMP, some even consider GIMP better.
I don’t think I have looked at Lightroom since 3, at the time, it could not easily print photos the way I wanted to print them. Photoshop could. Lightroom contains virtually the same ACR as Photoshop, so if most of your editing is done on raw files before conversion, they are equivalent. If you do much editing with layers, Photoshop is probably the tool.
If you are a professional and really believe GIMP is better, you might as well use it. If you are a professional and use GIMP because it is free and Photoshop requires payment, consider that the payment is smaller than the sticker price because you can deduct it from income before taxes, so you save the income tax, which varies based on your tax bracket. As there is a company behind Photoshop, there may be the perception support is easier to get.