SQL Query, how to know if is resource intensive? I/O

I am troubleshooting an issue with our marketing platform as it has become sluggish and slow, I've requested the top 50 heavy/resource intensive queries executed on our sql server to correlate with our marketing workflows. Here is an example or some of the top queries, based on the average I/O would you say these queries are consuming too much resources? what is a normal acceptable IO for a query? If I take the first query execution plan, it will be as following. Plan Link https://www.brentozar.com/PasteThePlan/?id=HJtGXHxUc