system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU/Captain Marvel] What are Skrulls made of?

Even in the 90s we pretty much knew the whole periodic table already. If whatever element is substituting carbon is completely unknown it is likely a transuranial element, or something formed by exotic matter (instead of protons and neutrons). 

What could possibly create complex life and not violently react with the water/oxygen combo of Earth?
gpt
The MCU periodic table is different from our own.  In Iron Man 2 Tony synthesizes a new element to power his Arc Reactor.  Very specifically it is called a new element, not an isotope or compound.  Meaning it has to have 119 protons or more.  But, any element with this many protons more than likely would have a very short-half life and be very unstable.  Essentially not acting at all like the element that Tony made. 

And at natie120 mentioned there is Vibranium which is an element whose properties don't make any sense based on our periodic table.

The only possibility is that while there is a lot of overlap the physics of their Universe is different from our own.  The Skrulls are just made of Skrullium or something, with physical properties that we can't understand.