You will be surprised to see the words "Simplicity" and "Complexity" together, but this is the fact for many things in the world. For example, the phone you use daily is simple in the interface but complex in design. Similarly, Islamic inheritance law is a divine law for Muslims and bears similar features you should know.
It gives rights to inheritance who need it, including spouse, children (and grandchildren), parents (and grandparents), as the priority heirs.
It's the same for every Muslim on the earth. Intestacy legal laws, on the other hand, differ from one country or jurisdiction to another. So, understanding the nature of the law will be easy because it is the same.
It prioritizes based on the roles in the family, i.e., financial vs. non-financial duties.
It builds a natural long-term link between the owner of wealth and the inheritors through Inheritance obligations.
It does not require any revision upgrades compare to legal laws, which keep updating over time.
The law is derived from four sources (Holy Quran, Sunnah, Ijma, Qiyas) which require knowledge and expertise for interpretations and learning.
The law has embedded rules and conditions that are complex.
The law may give different outcomes regarding Madhab (Hanafi, Shafii, Maliki, Hanbali).
The law may require interpretations in many special situations that fall beyond normal calculation methodology.
The law has rock-solid compliance guidelines. No Muslims can create estate plans to bypass Inheritance which may impact salvation. So, the following law is complex due to contemporary challenges and a person's situation and motives.