SLOW iMac

Confirming padams35's findings. CMM HAS to go. I've seen plenty of Etrecheck reports here where removing CMM actually let the drive run faster. Since about 2000, the macOS has, like a cat, cleaned itself with clever automatic maintenance scripts that clean, defrag, and optimize. Anything else interferes with that cleverness you paid Apple to develop and slows the computer.

Like my colleague,I don't think you bought enough computer for Adobe CS/CC. Not even a deity can increase RAM in a 2015 iMac. It is soldered in place.

As far as the drive performance goes, yours is a tad under max but close to observed averages:

Performance:

System Load: 1.81 (1 min ago) 2.30 (5 min ago) 1.98 (15 min ago)

Nominal I/O speed: 0.03 MB/s

File system: 48.43 seconds

Write speed: 60 MB/s

Read speed: 61 MB/s

However, like other 21.5-inch iMacs from 2012 to 2019 with that same 5400 rpm, 3GBps drive, it is slower than the factory drive in our 2011 iMac 21.5-inch:

Performance:

    System Load: 1.62 (1 min ago) 1.67 (5 min ago) 1.87 (15 min ago)

    Nominal I/O speed: 0.05 MB/s

    File system: 38.28 seconds

    Write speed:  112 MB/s

    Read speed:  91 MB/s

Removing CMM might help your scores but but that drive probably can't do over 80 MB/sec even in new, unfettered condition. These drive will cause slow booting and app launches and even if you could add RAM, it would not change that.

The external USB3 6GB/sec solid-state drive option is about all you can do cost-effectively and that would bump the drive performance to about 400 MB/sec

If you get a new 21.5-inch iMac, be sure to get all the RAM you can afford nd the biggest factory SSD. That will blow you socks off! IF yo ugo for the 27-inch, RAM is still user-accessible.

These are drive speeds in my 2017 iMac with a factory 1TB 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

SSDs are nice!

depending on the app 5sec is not that slow

and if it's an old magnetic 5400rpm harddisk then could be the cause

I would download the free app malwarebytes and try running it to check for malware and then I would download the free app etrecheck and run it and post it's result here

then people could see if it was 1 or several realtime virus scanners running slowing it down

NO! NOT CLEAN MY MAC! UNINSTALL!

FYI: CMM has a reputation of making slow macs slower, causing exciting new problems, and hiding so many pieces of itself everywhere that an uninstaller is required to remove it.

Which iMac do you really have? (There are no 2.3GHz 2015 models).

What screen size? Pure HD or Fusion drive? What software runs on startup? What software auto-runs in the background? How much memory (RAM) is being used?

I'd suggest posting the Etrecheck report, which answers all of the above questions and more. It's a long report, so use either Pastebin or the 'additional text' posting option.

Could be worse. You could have had the dual-core 2.3GHz 2017.

Issues:

1) 5400rpm HDD. These have always acted lethargic, but 5s to open a song is slower than normal.

2) No time machine backup. Sometimes computer die. Having a backup is good.

3) High CPU use. Maybe processes are just waiting on the HDD, but you might want to check Activity Monitor.

4) CMM.

5) Adobe Cloud. Some of those programs are very intensive and would benefit from a newer/higher-tier iMac with 16GB+ RAM and a 4GB+ GPU if you are frequently using advanced features.

Otherwise I'd suggest fixing item #1 by buying a USB 3 SSD and reinstalling or restoring MacOS onto that.