Core sync would like to access files on Macbook

just did some hunting and this is part of Adobe CC Suite to sync fonts etc. https://helpx.adobe.com/x-productkb/global/adobe-background-processes.html

so you can disable and not allow but you may experience CC sync issues.

Download and run Etrecheck.  Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

I have found this update has significantly slowed my iMac down. It is getting to the point where I will be forced to move back to Windows machines, iMac has now become so unwieldy, nobody uses the generic Apple work suite, MS Office is shockingly slow, Chrome cannot be used as it slows down my iMac

Core Sync seems to be related to Adobe Creative Cloud. So, it's "secure" as adobe products are. It also needs access to Downloads (or Desktop folder in my case) to go about its business.

Here are some folks discussing disabling it and the pros/cons.

https://community.adobe.com/t5/creative-cloud-services-discussions/how-can-i-disable-core-sync-and-updaters/td-p/7581821

Same here. I used to love Mac OS but it's incredibly slow now and I can't modify any computer parts. The whole verifying apps before opening them is a horribly inefficient approach. Mail always has issues and office is incredibly slow to open any apps.

My computer keeps crashing. I am a writer so it is detrimental. I update all day long, but I run so slow.