Unreal Engine is one of the most popular game engines available today. Moreover, it is completely free and open source. However, you will have to pay royalties when you reach a certain amount of earnings from the game (this, of course, also applies to other AAA engines, for example, another equally popular engine Unity).
As some people know, you can write game logic in C++ in the engine. But let me reassure you: you can also create game logic in it using a visual programming system – Blueprint is a visual scripting language that allows you to write game logic without using programming languages. No matter how complicated or simple it may seem, it remains a very powerful tool that can be used to create almost anything: from a simple character or door opening to procedural level generation.
The Unreal Engine itself provides a certain set of tools that allow you to create something of your own without resorting to third-party software (excluding textures). Inside the editor, there is a tool called BSP, which allows you to design a scene. Although it is intended for designing, not for the final result, you can use it to create a simple model and even convert it so that it can be subjected to physics. You can make a building, some not very complex models, and so on. It also provides tools for creating landscapes, with the help of which you can make a pretty beautiful landscape and enrich it with vegetation and some additional details. By adding a little post-processing, you can get a great picture.
Of course, you shouldn’t think of UE4 as a set of buttons called “make everything good”. The tool is very powerful with impressive functionality, so you won’t be able to learn everything at once either. However, if you manage to set a goal and have enough patience, you will succeed.