tell that to the guys who wrote worms.
seriously. I own a LOT of engines. They haven’t all been the best tool for my needs, but game development engines only come in three flavors: “Bare Metal”, “Pipeline Driven”, and “Just Add a Splash Screen”.
“Bare Metal” engines are source code based and usually use a custom set of formats with their own proprietary converters. You need to compile everything, every time you change it, and sometimes even redelpoy it just to test it in-house. You’re lucky if you have a gui level designer and a graphics format that you can actually read with photoshop. You can do anything with them, but they take nothing for granted, so you will spend most of your time inventing wheels.
“Pipeline Driven” engines are well suited for the formats they handle so its easy to produce content for them. They are the hub around which the stuff goes in and the games come out. They assume that you live on earth, you will be using industry standards, and the standard tools that create them, and you can focus on play mechanics and fun, instead of basic functionality. You can usually do just about anything with them, but some knowledge is usually required to use them to craft your ideal game.
“Just Add a Splash Screen” engines, are almost exactly that. Sure, you can usually create custom sprites and even some artwork, but these tools are designed to make a very specific type of game and are only well suited if that’s almost exactly what you plan to do with it. When you want it to do something outside of it’s intended functionality, you are almost always out of luck. The play mechanics have already been designed and you are simply a content developer.
Sure there are some that have elements of some or all three of these. But it sounds like you are looking for something in the lower pipeline/upper JAaSplash category. I have never seen a “Worms” genre development engine.
Unity falls somewhere near the top of the Pipeline variety. A considerable effort has been made to offer us the flexibility and functionality to craft our own play mechanics, without making us do it all from scratch. I know its discouraging to learn that you have to craft the parts that make your game so great, but knowing that you can do it is more than worth the work.
You can change things that don’t act the way you expected. That is the exciting part. It’s in your hands and not up to the whim or even spare time of someone who may be developing your livelihood in his spare time. I had to give up my favorite programming IDE because it got sold to a guy who didn’t like his users or have time to develop the product.
If you want my advice, you should put a few miles on Unity. Take it out for a spin and see how it handles. I’ve been doing this for a long time and I am using Unity for a lot of very good reasons. Of the game dev tools I have seen/owned, Unity is the best.
Unity may not seem well suited for your game ideas, and it may mean that you have to use a different method to reach your goals, but I’d be surprised if you couldn’t make something you were very happy with. (You may have to substitute pixels for particles or even polygons, but you’ll have a great time figuring out how to get it to do what you want).
But you probably shouldn’t ask me. 
It works for me, but your mileage may vary.