I doubted a lot whether to share this, my opinions related not to COVID 19 but to the insights that COVID has brought us. 

I consider sustainable a tourism that is collaborative with the local community, environmentally friendly, and tourism that is inclusive and accessible. A more collaborative approach to with the local community, for example, make it easier to develop a strategy that helps you in normal circumstances. When extraordinary circumstances, like COVID 19 happen, you have a group of people and businesses that can try to support each other. 

A more environmentally friendly approach in the business, first of all, is better because it is good with the environment where we live, healthier, safer, even more beautiful. Also, in the medium and long term is helping the business with a lower fix cost. 

Another way the sustainable approach to tourism would have helped is through more inclusive tourism. Here let me clarify what a mean with the word inclusive. I refer not only to people with some kind of disabilities (physical or mental) that for many reasons can find it challenging to have a proper experience, but also not to target just who is already our type of guests. 

https://www.sustainabletourismworld.com/what-can-the-tourism-sector-learn-from-covid-19/