Hi ezrat, unfortunately you cannot completely disable the Exercise and Stand rings. You can try some/all of the following:
Set activity reminders
- On your iPhone, open the Watch app.
- Tap the My Watch tab, then tap Activity.
- Change your notifications and reminders. For example, you can disable stand reminders, daily coaching and goal completions reminders.

Read more at the Use the Activity app on your Apple Watch - Apple Support article.
Change your Exercise and Stand goals
You can set large Exercise and Stand goals, which will ensure that you don't get Goal Completions reminders.
Sorry there isn't a more straightforward answer right now. You can suggest this to the team using the Feedback - Watch - Apple page. If a lot of customers want that option and communicate it, there is a higher chance you might see it on a future watchOS update.