I found its use of inheritance very confusing; could be quite hard to figure out what something does exactly because it could be in one of the 6 parent classes. The experience turned me off from OOP for many years (later nuanced to just inheritance rather than all of OOP).
I was also very much a beginner back in the late 90s/early 00s (my only previous experience was BASIC), so I'd probably struggle less now, but from what I recall it definitely overdid it on the inheritance (which, to be fair, was still fairly new back then).
That is just Unreal Engine in general, UnrealScript just exposed the C++ classes. But UE's C++ classes have very deep hierarchies even in UE5 and many classes have tons of methods.
In general UE often feels like its programmers took all the best practices and then ignored every single one of them - which, considering how popular the engine is and for how long it had been around (the codebase started in the early/mid-90s), is a good indicator how much that stuff actually matter in practice.
I was also very much a beginner back in the late 90s/early 00s (my only previous experience was BASIC), so I'd probably struggle less now, but from what I recall it definitely overdid it on the inheritance (which, to be fair, was still fairly new back then).