In the recent release of clan war experience a golden opportunity was missed - making every star count.
My recommendation is to bump up the amount of experience needed to level up the clan and make every star worth some experience. People today don't bother with all the stars if they are winning. I agree, why waste resources if it doesn't gain anything.
Therefore, something like this would be interesting as a baseline:
1 star - 2xp
2 star - 3xp
3 star - 5xp
Granted, the tougher the base the more experience similar to what it's already like today. But this way there will be additional incentive to 3 star every base (or at least try to) on the map.
And don't get rid of the total star bonus in the process.