Slow intel iMac

Remove Adobe Flash.

Using Virtualbox, VMware, for any other reason than to run Windows or Linux can cause problems. Mac OS X is not designed to run well within virtual environments.

Remove printer drivers not in use. You have Canon, Epson, HP, and Lexmark installed.

Apple menu -> System Preferences -> Printers and scanners show any connected printers.

Aviata is a special Epson software you have installed. If you can find its source application use Reggie Answorth AppDelete to remove it unless you are doing RIP processing. Third party printer drivers can be more of a pain than they are worth.

Cleaner One Pro (6.3.6)
is not needed and may actually be slowing down your Mac.  Use AppDelete to remove it as well.

That hard disk drive's performance seems slower than it should be, which would support my suspicion it needs to be replaced.

Diagnosing a failed hard disk drive is not a straightforward task. The best way to confirm or refute that assumption would be to connect an external hard disk drive, install macOS on it, and compare its performance to the internal drive.

Hard disk drives don't last forever. If that is that iMac's original one it's getting to be near any spinning hard disk drive's expected EOL. They can be replaced but it's up to you to determine if that Mac is worth the investment.

Definitely get rid of any and all non-Apple "cleaner" apps. Those things don't help and can only accelerate hardware's eventual demise.

Your iMac is definitely fixable, but different people have their own tolerance for the time and effort they want to devote to it. If it were mine I'd definitely install an aftermarket SSD from OWC / MacSales, which will make it run literally better than new. As such modifications are considered "unapproved" we are prohibited to offer much more than that advice, but OWC's website has instructional videos so that you can decide for yourself whether it's worth the effort.

Personally I like all 27" iMacs and think they're worth fixing. I definitely do not like spinning hard disk drives though, and won't miss their demise one bit. Apple has been developing the past several macOS versions specifically with solid state storage in mind. I haven't purchased a single Mac incorporating hard disks since about 2008. At that time, they worked well.

When I wrote that your Mac's hard disk drive performance "seems slow" it's because I don't have any to compare it with. It may or may not be a sign of hard disk failure, but read / write speeds of 76 and 91 Mb/s are abysmal by today's standards.

Etrecheck - the handy reporting tool for … - Apple Community

Make sure you remove any optimizers from your system. Advanced Mac Cleaner, and Mackeeper are notorious for causing crashes like this. Use Reggie Answorth AppDelete to delete any applications that are excessive third party applications you don't need.

Please determine if the same problems occur in "Safe Mode": How to use safe mode on your Mac - Apple Support.

EtreCheck is likely to reveal some actionable information as well.

Posting the EtreCheck report is likely to reveal additional information (you have to use the "Additional Text" icon below) but the fact it is performing poorly in "Safe Mode" almost certainly indicates that Mac's startup disk is operating in a state of failure.

They can be replaced. Contact Apple Support to determine your options.

Post the EtreCheck report.

Great news! Thanks for the update.

The M1 is indeed ridiculously fast and eclipses anything Intel has to offer. I think the internal hard disk was on its way out. If you decide to replace it with an OWC SSD that 27" Mac will be very much in demand. Just be sure to follow What to do before you sell, give away, or trade in your Mac - Apple Support, even if you were to give it to a close friend or someone in your family.