upgrading iMac 2012

A late 2012 iMac can be upgraded to Catalina 10.15.7 but no later.

Also see the following from Identify your iMac model - Apple Support

iMac (21.5-inch, Late 2012)

Model Identifier: iMac13,1

Part Number: MD093xx/A, MD094xx/A

Latest compatible operating system: macOS Catalina 10.15.7

Apple is offering a way to get a new or newer computer so that sounds reasonable to me for a 13 Year Old Computer

If the user whats the latest and greatest versions of macOS all is not lost.

If the user wishes to explore the Apple Trading In option where the Value of the exiting machine could be used against the cost of a new Apple Computer 

Or Shop Refurbished Apple computers at an Apple Reduced Cost

Have used both previously and have been satisfied each time.

Have Traded in iPhone 12 Mini for the latest iPhone 14, an iMac from 2012 for a M1 Mac Mini, an Intel Retina MBA 2018 for the M1 MBA

prasad2144 wrote:

I am just wondering, is Apple preventing this upgrade to force users to buy new hardware?

A 2012 Mac is 11 years old. The hardware is incapable of handling the newer features of the MacOS. Hardware that old can fail anytime. So continue to use it but be sure to keep current backups.

10.15.7 is not a bad MacOS, you can do a lot with it. I have newer Macs with the latest (Ventura) as well as a 2010 MacBook Air (High Sierra), 2013 MacBook Air (Big Sur) and a 2015 iMac (Monterey).

I can't read the mind of the architects who plan the capabilities of the newer models and of the newer MacOS. I suppose it is POSSIBLE this is some scheme to make users buy new hardware. I think what is more likely is that the market for computers is very competitive and Apple computers need to offers users computing power and capabilities that will motivate them to keep purchasing Apple products, versus other platforms. This leads to advancements that older Macs and MacOS cannot handle.

Some products, like TurboTax, now require Big Sur macOS 11 or later to even run. But I think you can still run modern versions of most products like Adobe photography and video and Microsoft Office with 10.15.7.