I don't know where I found it, but turning off FXAA for the program involved will usually solve it. I was having the blurry launcher as well, but turning off FXAA fixed it.
For NVIDIA, to turn it off, you will need the NVIDIA control panel installed. That should be installed alongside your graphics drivers.
You'll need to go here (Manage 3d settings and then select the 'Program Settings' tab in the right pane:
View attachment 959100
Once you do that, you'll need to find the launcher. It's easier if you start the launcher first, then close it (so it gets added to 'Recently Used'). Click 'Add' next to where it shows the program selected to get a popup to select a new program (this may take a while and appear to freeze for a bit if you have a lot installed):
View attachment 959101
Select the Paradox Launcher and then Add Selected Program. Then, where it says 'Antialiasing - FXAA', set it to off (my screenshot hides the program name because it has my real name in the path):
View attachment 959102
In the bottom right (not shown in the screenshots) there is an Apply button. Click it (may take a bit to process) and it should go away. That's it. Close the NVIDIA Control Panel and try the launcher again. This always solves it for me and it works for almost every program that has this blurriness.
With respect to the Paradox launcher, I'm not sure when it started, but it didn't always have this issue. At some point, I would assume updates to the launcher included something that change/improved antialiasing and that caused the issue. I don't have an AMD or Intel card, but you might google solutions for turning off FXAA for those to solve the issue.