When I search Python I should get the programming language but when my neighbour searches Python he should get snakes. That is a valid use of personalised search.
If the query is just 'python', then both you and your neighbour should get some links for the language and some for the animal.
If it only gives you the one you already know about, it's a useless tool.
Good example, which is why both you and the other commenter gave it. And if that's as far as it went it wouldn't have bothered me so much; it was when conservative people I know were getting different results from liberal people for the same search terms that I started to realize the potential for an echo chamber, and decided it was a bad idea.
It's good for your mental health to be exposed to arguments you disagree with. Many times they will be bad arguments and you can dismiss them, but it's good to know what the people who disagree with you actually believe. And sometimes, just sometimes, you might see something that makes you realize that it's your own worldview that was mistaken, and adjust your worldview to better fit reality. If your search results only show you echo-chamber results that already agree with yours, you'll rarely learn the areas where you were mistaken. (And nearly everyone is mistaken about some things; the person who is right about everything is a rare creature indeed, and you should never gamble that you're that person).