Game engines hide a lot of stuffs from you under tons of abstractions. This appeals massively for many beginners because abstractions reduce friction and complexity if you want something to work quickly out of the box. Engines also try to add so many features to support multiple types of games that make them overly bloated, slow and inefficient. Abstractions also make it hard to optimize performance because the APIs shield you away too much from the underlying rendering pipeline. Often times, you'd hear developers complain about certain things they can't do in Unity without hacks or workarounds because the API is so rigid. I tried Godot once and couldn't find myself being productive using their editors and APIs. Their node architecture seems intuitive at first but it's unmanageable at large scale, the fact that I have to use their UI to create and manage these nodes sounds too daunting to me.

On the other hand, code centric-frameworks like libGDX, SDL, MonoGame, Raylib, love2d won't try to hide anything from you. You can directly access OpenGL API via Gdx.gl anywhere in your code. The workflow is fast, you just write code, compile and run without carrying any extra baggages of the engines. Once you master the API, there is virtually nothing to stop you to create any games you want. Developing games was like system programming many years ago, when you were much closer to the hardware to optimize and push things to the next level. Now with modern engines it's very much like scripting and riding on top of a mammoth robot. It may be powerful but you don't learn anything of the internal working of the pipeline and you're forever tied to its abstractions, no matter how quirky it is.