How do I use high quality tiled backgrounds?

I’m working on a game (duh), and when i use tiled backgrounds, they look really bad quality. Here’s an example:

On the left is a tiled background, on the right is a sprite with the same texture. is there a way to fix this?

They're both upscaled from the looks of it, so that means you have to upscale the source texture.

I'd say at least doubled, if not quadrupled.

When i upscale, it makes the tiles huge, and i can’t make it smaller.

It's either that or change the scale of the game.

The viewport automatically scales to the size of the monitor when in fullscreen.

If you make the window bigger it won't have to upscale as much to fit.