Should I persist in updating Microsoft Powerpoint or is Keynote the better choice?

If you don't already have Powerpoint running on Monterey, you can use it for free on Microsoft's Office for Web applications. You will just need a Microsoft account and access to OneDrive. If your expected to do the presentation in Powerpoint, especially if you plan to share it with other Powerpoint users, then use Powerpoint.

Apple's Keynote is not a Powerpoint clone and there are differences in the applications, though Keynote can export its content to Powerpoint, where the same features are available in the Microsoft application.