I don't ride in groups often. Usually only for the organized century rides I do a few times a year. Otherwise I'm solo most of the time since I prefer to ride midday. And the others I have ridden with prefer the early morning. When I rather watch the news and drink my tea or coffee. Which gives the sticky morning air time to dry out.

So yes I still sprint up hills most every ride and on a few false flats. As well as the last quarter mile stretch to my home. Which frequently even after 90 or 120 minutes of riding is the section I get my second highest 30 sec power output.

But for a group, if the group wants to only do steady paces, then maybe it's time to find or create a new group. Have you ask them why they don't add a few sprint points?

Nor do you have to always ride with the group. Especially if this is a once a week group ride. You should be going out several other times during the week on your own or with a few others. Then you can more easily do what you want and sprint.