Why can't I update my Mac from macOS Big Sur to Monterey?

That model originally ran OS X 10.9.4 (Mavericks) – so from there, to Big Sur, it received a total of seven major OS upgrades.

Big Sur is no longer among "the most recent three", having fallen off that list about a year and a half ago. It is probably still good enough to run current versions of

• The Firefox web browser
• The LibreOffice office suite
• The GNU Image Manipulation Program (GIMP)
• The commercial Affinity V2 applications (Photo, Designer, Publisher)
• The backup utilities CCC v6 (not current, but still supported) and SuperDuper!

These might help you to extend the useful life of the machine.

However, should you need or want to run a more current version of macOS, you might want to take a look at the current MacBook Pros and MacBook Airs, which are all based on M4-family Apple Silicon chips.

Big Sur is the newest version of macOS available for a MacBook Pro (Retina, 13-inch, Mid 2014). No more recent versions are, or will be, available.

Identify your MacBook Pro model - Apple Support

This computer Does Not Qualify to run macOS 12 Monterey

macOS Monterey is compatible with these computers

Purchase a New or Newer Computer

Explore the Apple Trade-In  Process where the Value of the exiting device could be used against the cost of a new Apple Computer, iPhone or iPad 

Notation - Some devices and depending on the computers age may have little to no value at Trade In time.

But at least the device will not arrive to the Land Fill Site and be recycled in a responsible way by Apple

Or Shop Refurbished Apple computers at an Apple Reduced Cost

Have used both previously and have been satisfied each time.