The preview of my scene suddenly changed to a worse quailty
I dont remember touching anything, I just started daz and suddently it looked worse than before here are some examples. I tried to recreate a screenshot I had from before the issue, and as you can see, one looks more detailed and with better lights than the other

Comments
The first is using the Filament Drawstyle, the second Texture Shaded. You may have hit ctrl 9 when aiming for some other combo. Click the sphere icon to the left of the Camera/View button ("Perspective view") and select Filament again.