I think are right but not because of the size of the internet. Although the web has grown, the cost of computing and bandwidth has decreased and there’s a lot of open tools, technologies, and open datasets like YaCy and Common Crawl. The data you would want to index is a tiny fraction of the total internet.

The challenge comes from the massive investments in turning that data into a good search engine and cutting through spam. That is the investment I think Google has scaled over time. Secondly, mind share; the moat Google has is immense, although I think DuckDuckGo and Bing has shown given enough time it is possible to get mindshare slowly; though if anything this demonstrates the challenge.