Slow / "poor performance" - etrecheck results

It appears you did not buy an Apple refurbished iMac. I would STRONGLY recommend that you return the computer as it was not refurbished correctly or at all! Apple is the only organization that offers genuine certified refurbished Macs and they have not sold a 2017 21.5" as a refurbished device for years! If you want a genuine refurbished Mac please click Certified Refurbished Products - Apple . What you bought was a very used iMac! When you buy a Mac PLEASE never ever purchase from:

• Ebay
• Craigslist
• Marketplace
• Amazon
• Nextdoor
• Local PC Shop
• Friend, Neighbor or relative

Why, for exactly the reason I stated above. More often than not these machines were fixed with low quality parts and you are simply inheriting another persons problem. In addition we see on these forums that most of the machines sold as "refurbished" are not and have not been setup correctly correctly per What to do before you sell, give away, or trade in your Mac.

Finally if you cannot buy a genuine Apple refurbished Mac then buy a used Mac from a reputable source such as Macsales.com.

As for your EtreCheck report, it appears okay. The machine you bought was barely over a base model 2017 (now considered vintage and obsolete) that has a very slow 5400 RPM HD and small SSD that is supposed to be a Fusion Drive. These machines were designed for very basic computing, such as web surfing, e-mail and that's about it. Anything else and you were taxing their abilities!

Return it. Not only is it not refurbished, it is very much used.

By describing it as "refurbished" the (presumably) Amazon Marketplace seller is being disingenuous at best. Fortunately Amazon's return policy is very generous.

Performance:

...

File system: 56.23 seconds

That's bad. I do not recall such poor performance from those Macs even when they were new. It has been nearly six years since they were discontinued.

1) That base model 2017 21.5" iMac's was a slug when it was new.

It was ment for entry level users to surfed the web and do light photo work.

2) That iMac Fusion Drive is split and it is only running from the slower 1T HDD.

see > How to fix a split Fusion Drive - Apple Support

3) That 2017 iMac is considered Vintage and will soon fall into the Obsolete category.

This means that it will no longer receive security update or run newer App's from the App Store.

My advice is to return that iMac to the Amazon seller and buy a 2019 or later refurbished Mac from OWC or Apple.

https://eshop.macsales.com/shop/Apple_Systems/Used/Macs_and_Tablets

Refurbished Mac - iMac - Apple

I'll add my 2¢ worth to the excellent advice you've already been given.

Return it for a full refund!!!

If budget is a primary concern get a refurbished Mac from either Apple or OWC (MacSales.com). OWC is the only 3rd party vendor I would trust for a refurbished Mac other than Apple or for add-ons to a Mac.

Do not get a refurbished older than a 2019 Intel iMac. Anything older will not be able to run the newer systems and will be obsolete shortly.

Do not get less than 16 GB of RAM and only an SSD for the boot drive.

Here's some food for thought:

You can get a new Mac Mini M4 with 16 GB of RAM and a 256 GB SSD boot drive for $600. Combined with a 3rd party monitor for as low as $100 on up you can have a very fast, modern Mac that can be current for years to come.

Your welcome, glad you were able to return it!