Even though I miss using boolean operators in search, I doubt that it was ever sustainable outside of specialized search engines. Very few people seem to think in those terms. Many of those who do would still have difficulty forming complex queries.
I suspect the real problem is that search engines ceased being search engines when they stopped taking things literally and started trying to interpret what people mean. Then they became some sort of poor man's AI. Now that we have LLMs, of course it is going to replace the poor excuse for search engines that exist today. We were heading down that road already, and it actually summarizes what is out there.
People were learning. Just like with mice and menus, people are capable of learning new skills and querying search engines was one. I remember when it was considered a really "n00b" thing to type a full question into a search engine.
Then Google decided to start enforcing that, because they had this idea that they would be able to divine your "intent" from a "natural question" rather than just matching documents including your search terms.
I suspect the real problem is that search engines ceased being search engines when they stopped taking things literally and started trying to interpret what people mean. Then they became some sort of poor man's AI. Now that we have LLMs, of course it is going to replace the poor excuse for search engines that exist today. We were heading down that road already, and it actually summarizes what is out there.