There's an irony here -- the same tools that make it easy to skim and summarize can also be used to force deeper thinking. The problem isn't the tools, it's the defaults.

I've found that the best way to actually think hard about something is to write about it, or to test yourself on it. Not re-read it. Not highlight it. Generate questions from the material and try to answer them from memory.

The research on active recall vs passive review is pretty clear: retrieval practice produces dramatically better long-term retention than re-reading. Karpicke & Blunt (2011) showed that practice testing outperformed even elaborative concept mapping.

So the question isn't whether AI summarizers are good or bad -- it's whether you use them as a crutch to avoid thinking, or as a tool to compress the boring parts so you can spend more time on the genuinely hard thinking.