I'd love the answer to be a
heart
You are what you eat, so I suspect you like sweets, for I think that’s what you are.
you think they are a sweetheart (also a candy), and heart contains 'are' rearranged
A plain figure you have, with rounded sides, a symbol quite bizarre.
the $\large\color{red}♥$ symbol, (a stretch produced by keypad Alt + 3 is alternative odd) - I'm missing a clue here
I hear the mad hatter gave up tea for you, and you’re hiding in plain sight.
anagram hatter - t = heart, and hiding in: I hear the
You may be arrested if you push too hard, or are taken afright.
pushing too hard or a fright may cause a cardiac arrest
But I would move the earth for you, or then again, maybe not.
anagram earth to heart, but you don't want the anagram to be hater
Title: An easy riddle at its core
the core is the heart of this matter