Airlines are subject to EU law and the rules of the Civil Aviation Authority.
When you book a flight, you are entering into a contract with the airline. If they cancel a flight, they are breaking their contract with you and are therefore responsible. Travel insurance does not cover this situation, which is why you need to address the issue with the airline.
If you are affected by Ryanair cancelling your flight, they are required to:
If you accept a refund and then book a flight using an alternative airline, it could be difficult to go back to Ryanair and ask them for any difference in price.