Xcode is taking few minutes to preview or to run the scheme of a basic app. I have been having this issue since I upgraded to BigSur and Xcode 12. Xcode worked fine before that.

I am using Macbook Air 2017. Is it possible to fix this issue? Should I buy a new Macbook?

I'm on a 12" Macbook right now and the previews are also really slow for me so I stopped using them. I still keep the preview methods working though so that when I eventually upgrade they'll all be there, but in theory you can just delete the preview structs.

Xcode itself is heavily CPU intensive, with the macbook air having no active cooling it isn't ideal. I was using a MBP 13" i5 8GB and still it was painfully slow. I was an early adopter of the new M1 mac and the speed has increased significantly.

I would highly recommend buying a new mac but if you can wait Apple will be releasing an even better silicon which is rumored to be called M1X which is going to be even faster.

I can't stress enough how much more motivated I feel working on a faster machine.

in theory you can just delete the preview structs.

I have noticed that previews appear faster on my device (iPhone SE '20) than on the my mac (MBA 2013). Can i just disable the previews on the mac and keeping getting them on the iPhone?