Hi Don A. Duncan!
Thanks for sharing your comments and screen shots. In reference to what you're seeing under the "About" menu drop-down, I never see the "Update License" link in the Outlook application. This link only appears in the "About" menu drop down for the Excel, Word and PowerPoint applications. In the Outlook application, the "Update License" position is replaced with the notion that I am using the "Legacy Outlook" version (instead of the so-called "New Outlook" version. Since you're on Version 16.78.3, you may not have experienced the opportunity to make the switch to the new version of Outlook (which in my opinion, is pretty awful). Fortunately you can opt out and continue using the legacy version of Outlook. Sorry I wasn't more clear about that earlier.
Just to clarify further, here is what I see in my About Outlook window ...

And here is the About Outlook drop-down menu, showing the "Legacy Outlook" text ...

Next up, here are the "About" menu drop-downs for Word, Excel and PowerPoint, all of which show the "Update License" links ...

Because I'm using the very latest version of Office H&B 2021 for Mac {16.82.2 (24021116)}, when I open any Office app and go to the help menu and select "Check for Updates", I see this:

I just checked out our iMac Pro and its Office H&B 2021 apps are all at the current version {16.82.2 (24021116)}. I ran the AutoUpdate and it was the only app that needed an update, from version 4.67 (installed on Jan 18, 2024) to version 4.68. So the iMac Pro matches the behavior of my MacBook Pro. That said, as the AutoUpdate ran, I observed that the iMac Pro also has Microsoft Defender, OneNote, Teams Classic and OneDrive installed. I'll be uninstalling these unused apps ASAP.
Regarding your remaining observations on what's going on, I agree that Microsoft definitely seems to be moving towards subscription-based products. It could very well be that Office 2021 for Mac is basically a rebranding of Office 2019, with a few enhancements, like the introduction of the "New Outlook" and other tweaks throughout the range of apps, including the 4 above that I'll be removing. I've used the Office product line for many years, starting with Office 2011, through 2016, 2019 and now 2021, and have had very few issues or complaints in all that time. My next-door neighbor has a 2013 vintage iMac and has been running Office for Mac 2011 ever since. I'm amazed it still works, but it does (and they never get any reminders about needing updates!).
There's an interesting "End of support resources for Office" dated 12/12/2023 that offers some insight into versions that are no longer supported. the potential risks involved, and as expected, recommends upgrading to Microsoft 365 Apps. From my perspective, if there's not a comparable one-time purchase Office Home and Business product from Microsoft to replace the 2021 product in 2026 (or whenever), I'll very likely migrate to the Apple equivalent apps (i.e., Numbers, Pages, Mail, Keynote). I have zero intention to migrate to a subscription-based product.
Lastly, the 2021 Home and Business for Mac product is indeed listed on Microsoft's web site, as noted in the following screen shot ...

I purchased this version on our iMac Pro directly from Microsoft in August 2023. The version on my MacBook was purchased from Best Buy when I purchased my MacBook Pro there in July 2023. There is virtually no difference in the products with the exception that the purchase directly from Microsoft has a one-year warranty, versus 90 days for the Best Buy purchase. I can't imagine the hassle that getting a warranty claim handled would entail in either case.
I suspect that a number of visitors to this thread will say or think TL;DR. Hopefully, the content will be useful to those who may be seeking to understand and resolve the issues of the type we've encountered with the 2021 Office product.
Ciao!
Don