I could do that in a weekend

Where Google devastates other search engines is ability to get revenue from advertising.

Bing used to look like it had an ad load equivalent to Google but it was getting much less money per ad so Microsoft has really been running a charity. Today I see a very low ad load on Bing so I think Microsoft has given up on trying to look like they're successful at selling ads.

It would be quite possible to get better search results than Google today because the advertising gives them a powerful incentive to degrade the search results to train you to click on ads instead.