If I create content like recipes, journalism etc, previously I had exclusive rights to my created content and could monetise it however I wanted. This has mostly led to what we have today, some high quality content, lots of low quality content, mostly monetised through user hostile ads.
Previously, if I wanted to take a recipe from "strawberry-recipes.cool" and published it on my own website with a better user experience, that wouldn't have been allowed because of copyright rules. I still can't do that, but Google can if it's done through the mechanism of AI summaries.
I think the worst case scenario is that people stop publishing content on the web altogether. The most likely one is that search/summary engines eat up money that previously came from content creators. The best one is that we find some alternative, third way, for creators to monotise content while maintaining discoverability.
I'm not sure what will happen, and I'm not denying the usefulness of AI summaries, but it feels easy to miss that, at their core, they're a fundamental reworking of the current economics of the internet.