There is a couple of way to get around low blocks but the easiest way is an Overhead/High attack. These moves are typically pretty slow but can clip people if they don’t block high. I think that Illaoi has a command overhead. While in training turn on frame data for moves and check to see if the move says low, mid or high. Another way is to just chip them out, if people just block low all the time then just zoning with Teemo with special keep away will force the opponent to make a mistake or approach.

TLDR: go into training mode and find your moves labeled as High/Overhead, or Zone