1. Google is proposing to limit the API uBlock Origin uses, and replace it with a less capable one.
2. Google also plans to put artificial limits on the new API (30,000 rules or something), which will make it even more difficult to make an effective ad blocker. That's not even enough to implement current blocklists.
3. The new API is inflexible, so it will be difficult to impossible to create innovative ad blockers in the future.