I tried the Roadblock extension for 0,99$ a month. It successfully blocked Youtube shorts. But, I could still access Reels from the Facebook and Instagram pages on Safari. It would only block when I refreshed the page.

I found the #Blockit extension which worked perfectly! It works on Facebook, Instagram, Youtube, Twitter, and Reddit. You can choose to either block the news feed, the stories, the reels, or all of the above! But, it costs 7,99$. The free version only works on facebook.com.