I guess it depends on the component parts of your trip and the modification options. For a domestic trip, how are you able to cancel each thing? Are you booking a package?
I always book everything separate - tickets, hotel, flights. With flights, I can modify without penalty (just fare difference) or cancel and get a flight credit. With tickets, they don't expire until January of the following year and you retain the value even if they do expire (I buy through a third party). For hotel, I stay offsite usually and I'm not charged until check-in, and cancellation policy where I stay is 3 days in advance for 1 night.
For
travel insurance, read the fine print to make sure what you want covered is covered. At a minimum of $100 (or more), the only risk for me is 1 night of hotel. I don't really see the value in travel insurance for a trip to
Disneyland.
Yes, flight cancellations or delays could happen. I book on a credit card that will reimburse me partially for a trip delay. For example, $500 if I can't fly in until the next day. This is better IMO than travel insurance.
If doing a cruise or international trip, my opinion about travel insurance changes - particularly locations with the potential for severe weather.