[Exported files coming out blurry on social media]

I have been using Affinity Designer for a little while now (still quite new to it) and use it to create posts for social media. Recently every time I export the files to post, they come out blurry. It's a square post so I have done 1080px x 1080px, 96 DPI, and exported them as a .jpeg file as those are apparently best for social media. Have tried various other resolution sizes and DPIs and exporting as a .png file. Every time we post though it to Instagram and Facebook, it comes out in terrible quality. I was wondering if there's a very simple solution I'm missing?

Thank you!