Posting the EtreCheck report here give us computer details you have not shared, like storage configuration and possible software conflicts.
Minis in 2014 had three storage configs:
- a standard mechanical hard drive;
- an optional Fusion( hybrid) drive;
- and an optional solid-state drive (SSD).
Those drive options are at the heart of ~95 percent of "Slow Mac" complaints here.
A factory SSD or a healthy Fusion drive should not feel sluggish even with a newer macOS version. The slow factory-standard mechanical drive is almost always the culprit. However, Fusion drives can have issues that slow performance.
Software conflicts are rife, given the amount of useless "utilities" sold by fear marketing.
Posting the EtreCheck report here is how the utility was conceived and intended to work, We senior contributors have interpreted thousands of EtreCheck results and can quickly spot issues that may not be apparent to non-technical users.
Best of all, you get diagnostic confidence in a very limited support setting. Without EtreCheck, all we can do is give you generalities; with it we can give diagnoses based on data, not guesses. That is otherwise not possible in a setting ( this one) where we can neither see, touch, nor remotely access your Mini.
