Updating from CS6 master collection...new subscription version apps require internet?

You need a stable Internet connection to download & install apps and again to update them. 

You also need Internet for a few seconds each month to verify subscription status or every 90 days for pre-paid annual plan. 

But the other elephant in the room is access to your online services like Creative Cloud storage, File synching,  Adobe Stock images, Adobe Fonts, Adobe Portfolio, etc...  Without Internet, you won't be taking full advantage of your plan's benefits.

Is it worth it?  Only you can decide that.

Make sure your computer meets the minimum CPU & GPU requirements. Most Creative Cloud apps work on:

• Windows 11 (64-bit), Windows 10 versions 21H2, 21H1, 20H2, 2004, and 1909 (LTSB branches are not supported;)
• macOS 12 (Monterey), macOS 11 (Big Sur), macOS 10.16 or 10.15 (Catalina).

https://helpx.adobe.com/creative-cloud/system-requirements.html

If you never have any internet connection at all, ever, then Adobe Cloud apps will not work for you due to the periodic mandatory activation checks. 

Creative Cloud apps will periodically contact the Adobe servers to confirm that your subscription is current. This is automated, invisible to the user, requires an internet connection and generally takes seconds.

In your situation, there are grace periods for offline use before an activation check is required. These periods vary depending on your subscription.

See https://helpx.adobe.com/au/creative-cloud/kb/internet-connection-creative-cloud-apps.html

Once the grace period has elapsed, the apps will stop working until an activation check is successfully performed. This could be as simple as signing in while visiting a cafe with wifi or using a prepaid portable modem.

I don't know the time period (I am always connected) but after "some" amount of time the subscription will stop working if a connection is not made for verification