They change the value of every organic position on the page, which is why a forecast built on a generic click curve overstates traffic on feature-heavy queries. Before committing to a keyword cluster, run the searches: the presence of a map pack, a shopping carousel or an AI Overview tells you more about achievable traffic than any difficulty score.
Some features are opportunities rather than threats. Image and video packs open positions to formats a text page cannot occupy; People Also Ask reveals the sub-questions your page should answer; a review-rich result changes click-through without changing rank. Read the SERP as a brief, not as an obstacle.