Your carry-on luggage has to be small enough to fit in the overhead bin. This is a fact, not an opinion.

Even though they sell expandable carry-on bags with all kinds of pockets and pouches and wheels, the laws of physics still apply.  You cannot fill that "carry-on" until it's bursting and then stuff it into the overhead bin on a plane.  The airline has a little box right near the check-in and at the gate that your bag has to fit in in order to fit overhead.  Ignoring that little box will not alter physical reality.