You DO have other choices than to fly through a thunderstorm, or trying to land in one.
It has been mentioned, and I will repeat again, thunderstorms present great danger with wind shear, hail, lightning, and very strong vertical winds. They are to be avoided.
The greatest danger is their unpredictability. In a matter of 1/2 hour they can blossom into the severe category, which will be dangerous to any type of aircraft.
Also, be aware that radar information may not be real time, and in unstable air an apparent opening may close rapidly.
Regarding the scenario presented by the OP, these options can be considered:
Fly over the top of it. Severe thunderstorms can reach over 50,000 feet. Difficult.
Land, tie your plane down, and wait for it to pass. A thought, especially if there is a line of storms approaching. A few hours delay may save the air crew's lives.
Fly around it. This is the preferred option. Carry extra reserve fuel and be aware of the weather.
Important to realize thunderstorms are creatures of vertical airflow. Hail, turbulence, lightning, heavy rain can occur in any part of the storm. Because of the vertical nature of the airflow, strong downdrafts (microbursts) can crash a low flying plane, and turbulence can severely stress an airframe. Softball size hail and tornadoes are a testament to the forces involved here.
However, not all thunderstorms are super cell monsters like the one pictured. If the plane is built to handle it, with proper information and approval, it may be a "GO". But not without risk, which would also include icing.