In the real world Ukraine did a de facto draft of all men aged 18 to 60, refusing to let them leave the country—a less charitable way of putting it is that those men were taken hostage.
The “patriotic civilians fighting” is (for the most part) a parody of what is actually happening on the ground.
You are either uninformed our pushing Putin's propaganda. The Ukrainians have been in a low intensity war with Russia since 2014. Many young men have done their military service during that time, and are re-joining now to fight for their country.
If you watch videos from Ukraine you can see their military, local defense forces, and even militia fighters in action.