|I find overall that Google still (just) tends to return the most comprehensive range of results but that is less so than it was. It can often take scrolling through at least one page full of only marginally related adverts (sorry, 'sponsored results') to find the nuggets.
It does increasingly depend on how you ask the question too.
These days, even if you insist that the results must contain certain words in order to narrow down to a specific result, Google in particular will return many results that do not contain that word, possibly by using similar meanings or spellings?
Search used to be very 'serendipity' driven (can't think of a suitable word here), whereby you might often discover something different about a subject because the hits were somewhat random. Nowadays the engines are so focussed on pushing results based on what it is the engine thinks you are looking for (rather than what you are actually looking for) that you often end up with pages of irrelevant answers that don't contain known results you previously found.
This is the same 'feature' that causes you to see endless adverts for washing machines for weeks after you have bought one on-line - how many does the AI think one person needs! Woe betide you search for something for a friend that you have no interest in - for example I often buy historical ebooks for my wife through my account - guess what fills my feeds for days afterwards!
It's hard to express this clearly, but I think in an attempt to return more closely focussed results, search has gradually become less useful because the engine tries to eliminate things that it thinks are not relevant to the query you have made, and yet - for the more obscure subjects - those results are often the ones that lead you to an answer.