Although my cheap-ass laptop (Acer Swift One) scales without getting blurry, I can imagine that not all laptops are equal in that field.
The reason why scaling MATE can get blurry is this:
- Mate themes are bitmaps.
- Most themes are build for 96dpi pixeldensity which used to be the standard.
This is why it is not so simple to "implement fractional scaling on the fly" without losing sharpness,
BUT: You can try if xrandr scaling is more to your liking. Read this, especially the part below "Scaling the desktop with Xorg X11"
You could probably use the 200% HiDPI setting and then downscale with xrandr.
This would theoretically give a sharper image than upscaling with xrandr alone.
The other way, which seems to be the choice of several users, is to enlarge the default font sizes in "appearances" in mate-control-center and pick a XXL theme for bigger windowdecorations like buttons and titlebars, for example:
This will probably give superior results.
However, you probably need to do some extra work for GNOME applications because, contrary to the rest of the linux ecosystem, they use Client Side Decorations thereby completely sidelining central theme settings