A few things.

1. GOOGL is the voting share stock ticker, not GOOG. GOOG is nothing more than class c shares.

2. Search as a line item is more than 50%, but search is not searching, searching itself provides not much value, ads are where Google makes its money.

3. A stock being near all time high has no indication that it's a company that is "swirling the tank". Often a stock does not decrease until after a series of bad earnings/negative outlook. But with that said, there is no evidence at the moment that Google is not doing great.

This discussion is partly about how Google alters search results to increase revenue. It would stand to reason that they might also improve their stock price and search revenue by doing this, while also degrading search quality.

As for why their market share has not degraded as a result, it is likely that the folks currently prosecuting Google for antitrust violations have the best argument for why this might be so.

The stock price is a number representing the recent bets on its future price. It really doesn’t tell much more than that.

A stock price does not mean that everything the company is doing is perfect. It can reasonably mean « their search is getting worse but they’ve found very good ways to make more money from worse search so I’m very happy and will buy more stock».