Late 2012 imac running slow

[EugW]

El Capitan is our friend!
The only thing I miss from highest exulted Sierra is a better screen of movie streaming and pages simultaneously saving files on all the devices. But I do not miss the constant spinning ball.
Personally, I think elcapitan has good features h Sierra omitted like split screen and non Siri.

The spinning beach ball of death is likely due to insufficient memory. However, the OP has 32 GB.

IMO:

4 GB: OK for very light usage, but moderate multitasking can cause the spinning beach ball of death.
8 GB: OK for moderate business usage.
12 GB: OK for heavy business usage and other types of memory hungry usage too.
16 GB: Even better.
24 GB: Yet even better
etc.

The point I'm making here is that the slowdowns you are noticing in OS versions past El Capitan may be related to insufficient memory. Yes, Sierra is worse and an SSD would help, but if you have at least 8 GB RAM, then IMO it usually feels similar to El Capitan, and even High Sierra usually feels fairly close for mild to moderate multitasking of office type applications. And as mentioned, a clean install always helps.

 

[nambuccaheadsau]

The day of the platter and Fusion Drive are now gone.

Go with an SSD or PCI-e Blade Drive.

 

[MBAir2010]

My macmini has 4 happy gbs of ram that runs QuickTime, iTunes, photoshop, and other apps without beachballs.
Elcapitan is our friend!
And can be all yours as well