Why is my Mac Mini Late 2014 very/extremly slow?

Hi MarkB129,

I believe we need to proceed with an EtreCheck report. EtreCheck is a useful app to diagnose and identify issues, both hardware and software. It is trusted by many users. Please follow the steps outlined below:

1. Navigate to: https://etrecheck.com and get the free version of EtreCheckPro.
2. Download it. It is a free and trusted app. It is often recommended here on Apple Support Communities. 
3. Open EtreCheck, and before running the report, be sure to check “Allow full Drive Access” at the bottom of the EtreCheckPro window.
4. Run the report, and put it in a post, as seen here: https://discussions.apple.com/docs/DOC-250000211. We will then examine the report for issues in your Mac.

Cheers,

Jack

My two cents: I have the same machine (with the same "spinning rust" HDD) and it was also suffering from major slowness and frustrating loading times. I "solved" this by booting Catalina (clean install) off of a 500GB Western Digital Blue SSD 3D NAND in a USB enclosure and transferred only needed files and apps over to the "new" hard drive and kept the original internal HDD as a backup/storage device. Now it's snappy and quite responsive. Set the external up as the startup disk and bob's your uncle!

I know booting form an external drive is not everyone's cup o' tea, but this works just fine for me!

We don't have a crystal ball. Best guess, if you have the original mechanical hard drive, it's failing.

If you have a mechanical HD, I would recommend using the free trial version of: https://www.volitans-software.com/apps/smart-utility/

I have the same issue with my Mac mini Late 2014, Mark. Every application takes extremely long to load, Safari is slow, and generally all functions have slowed to a painful crawl. While I thank Lanny for his response, the webpage of the software he's suggesting says it's "For 10.9 to 10.15." I have 11.3 and see that you're on 11.2. I'm hoping that this problem is not the beginnings of hard drive failure, but then again, I do still have the original hard drive.

I attempted to run Disk Utility last night, but it crashed the system. I'll try it again today and will post my results. Any developments on your end?

Mark, Lanny was right. I took his advice and downloaded the software he recommended. It showed that my hard drive was indeed failing, thus the slow performance. I took the big step of ordering a new SSD (OWC 1TB Mercury Electra 6G SSD 7MM) bundled with an install kit and installed it myself. Wow, what a difference! From startup to login screen - 0:36 seconds. From login screen to full desktop - 0:27 seconds! Apple Mail, Safari, Microsoft Office, everything is incredibly fast. To Lanny - thank you!!

It is compatible with Big Sur: https://www.volitans-software.com/support/