Is Reality an illusion?
A small issue on nomenclature comes to play here.
If "reality" is meant to be these 3 + 1 dimensions called time and space, then YES!
If "reality" is meant to be infinite consciousness, then no. Your definition will make people tear up with joy every night when they understand this too.
People will have different definitions for what they call "reality" based on what paradigm they're on.
It's okay if this is a hard thing to understand at first, but luckily you can start to let go on unnecessary narratives that run your life by asking yourself " No matter Where you go, who you lose, who you gain, what you lose, or what you gain, what doesn't change?" It doesn't change the fact that you are here to create new experiences - exploring the world and cultivating it in your own way.