>since I noticed SeaMonkey made the text fuzzy
You're using some kind of high DPI mode. The default in modern versions of Windows is that "legacy applications" get crudely upscaled like an image if you're using anything besides 100% scaling (AKA 96 dpi)

Assuming you're on Windows 10/11 with a skin, you can right click a program/shortcut -> Compatibility -> Change high DPI settings -> High DPI scaling override, and try one of the other options. It's possible that the program does support higher DPIs, but not in the way that modern Windows expects

Alternatively, you can just go back to 100% scaling and choose a lower resolution if you want to make everything "bigger", which will also make all "legacy applications" look their best