I’ve played my fair share of video games in my life, and I don’t remember ever enjoying exploding barrel gimmicks. Then again, I hate a lot of other popular things, like steak and tube tops, so maybe I’m a horrible judge of what’s fun.
If you’re looking for a game that is fun despite a lack of exploding barrels, you should check out Villainous on Kongregate. It’s a reverse tower defense game where you have to lead your monsters through sieging different towns and castles. It has a skill tree, rainbows, is reasonably challenging, and is free. That should be all I have to say.