Hi TCCarnuel,
Thanks for posting the query here in the community.
I apologize for all the inconvenience.
Per your description,
slicers are blurry in Excel 365. We test in our side Excel version 16.33 PivotTable slicers, Table Slicers, and PivotChart
slicers can work as expected. See below is my test image.

To move further**, ensure your Office have the latest updates**. Here’s how to install updates:
In any Office application,
go to the Help menu and choose Check for Updates to launch the AutoUpdate app.
Let AutoUpdate install updates and then restart your Mac.
Also, You can set up Mac in safe mode according to this article:
Start
up in safe mode. This can help you troubleshoot whether it is caused by third-party software.
Disclaimer: Microsoft provides no assurances and/or warranties, implied or otherwise, and is not responsible for the information you receive from the third-party linked sites or any support related to technology.
If the problem persists, can you please provide the following information for moving further:
- Excel application version with detail build number. (Open Excel application> Click on Excel in Menu bar> About Excel)
- macOS version. (Click on Apple icon> About Mac)
- Do all the Excel documents have the same problem? You can create a new one to check if the same problem will occur. If
the problem only happens on a specific document, you can copy the content of problematic file and paste it into a newly created
file to continue the work.
Appreciate your patience.
Regards,
Waqas Muhammad