Welcome! Posting the Etrecheck report was the right thing to do. Problems identified in one post. Well played!
I see two issues, one of which ku4hx has already spotted.
First this:
Hardware Information:
iMac (21.5-inch, 2017)
Status: Supported
iMac Model: iMac18,1
2.3 GHz Dual-Core Intel Core i5 (i5-7360U) CPU: 2-core
This is the crippled educational/institutional iMac made to be atractively priced for bulk buyers. It has a laptop-class 2.4GHz 2-core processor. The standard consumer model that year, the 21.5-inch 4K, had a proper desktop-class four-core processor, the SLOWEST of which ran at 3.0 Ghz. The performance penalty with the edu-model was massiv. These are benchmark scores for your iMac v. the consumer 21.5" in 2017:
OK, you can't change that now. However, the second problem, the slow factory mechanical hard drive problem, is at least addressable. It is possible to make what you have work better for you.
Your drive performance:
Performance:
System Load: 1.93 (1 min ago) 1.85 (5 min ago) 1.83 (15 min ago)
Nominal I/O usage: 0.11 MB/s
File system: 42.52 seconds
Write speed: 80 MB/s
Read speed: 71 MB/s
Those scores are first-rate for that drive model, but are still dreadfully slow for todays apps and OS version. The fastest mech-only drive system score I have on record are still under are under 200MB/sec.
Modern iMac with solid-state drives (SSD) run over 2000MB/sec. My 2017 5k with factory SSD:
Performance:
System Load: 1.66 (1 min ago) 1.42 (5 min ago) 1.31 (15 min ago)
Nominal I/O speed: 0.23 MB/s
File system: 20.35 seconds
Write speed: 2156 MB/s
Read speed: 2863 MB/s
Apple Silicon Macs are now breaking the 3000MB/sec barrier.
The cost-effective fix that does not involve a new computer is to get an external USB3 drive containing an SATA 6GB solid-state drive. When set as the boot volume, it can do 400MB/sec and that is very noticeable in use. See this excellent user-submitted tip on how to do it.:
https://discussions.apple.com/docs/DOC-250003583
Depending on the size of the SSD, this can be done at home for under US$100.
Please post back if needed.
Allan