Pseudo-monopolies are great at extinguishing imagination like that, and tbh Google search (as I understand its basic setup) was only as good as it was thanks to timing and few really good competitors.
You absolutely can. I did, and plenty of other people do all the time about a variety of systems, search engines included. That's not to say they'll be good critiques, but that's irrelevant to whether or not they can.
And in that vein, I'm not suggesting mine is a good critique. However it is reflective of my opinions from my experience with their system and my admittedly rough knowledge of it at the time of writing. Instead of adding to dismissive replies, how about we all get together and read the PageRank wikipedia page and learn together.