I've never heard of RAWTherapee, I've always used Lightroom and Photoshop because of they're the best on the market with a ton of free support online. However, it certainly sounds like the program is applying a preset to make the image look washed out.
Check out the sliders/control. Once you open the image and it's washed out, make sure that they're all set to 0. A washed-out image is caused either by overexposure in the camera, or the settings of the image-editing software are too high. In your situation, it appears to be the software applying either a preset or a default setting to the image once you open it. Look for settings for exposure or brightness and you'll more than likely be able to fix the image. RAW images are also low in contrast, so you'll need to bump it up along with some saturation (but easy on the sliders).
It's common to go too far with your editing (i.e. overcook your images). This is especially a problem for those new to photography. The novelty of being able to adjust things and to make this so unique and colorful makes it very tempting to apply settings that are just way too strong. After working with an image for a while, stop. Get up and do something for a little while. This will give your eyes time to readjust so when you go back, you're looking at the edited image with "fresh" eyes. Most of the time when I do this, I end up backing down the sliders by 10-30%.
Go to YouTube:
https://www.youtube.com/results?search_query=RawTherapee
And watch all of the videos on RAWTherapee. Take notes and keep track of any new terms or concepts that you're unfamiliar with, and then do another YouTube search for those terms/topics. That's going to keep you busy for a good while, and with baby steps, you'll end up being pretty good at image editing within a month or two.
