How do we go about getting leader and others removed from alliance for not playing for more than a number of days.
You can’t. Only one that can control that is the leader themselves. (I’m sure the Devs could, but I’ve never heard of them doing it)
I’d highly suggest leaving your alliance and joining one of the many active alliances depending on your play style.
If you’re looking for daily activity on 7*/8* Titans. Check out Shadow Watchers by searching Watchers. I could fit a couple of your alliance mates too.
If your leader is inactive then you should form a new alliance and have everyone move over, since the leader is the only person who can kick anyone who is a co-leader.