Google is pretty good. Here are the things I find frustrating:
1) It tries to guess what I mean, and it's hard to make it change its mind. I was searching for a specific thing and Google decided I was looking for clothing brand in this colour. In the past adding or removing words, using the + (or "") or - operators would help, but I couldn't find the right combination this time.
2) Sometimes I want to search for results from a different country in a different language and I don't know how to do this. Google seems to really want to only push English language results to me. I don't know if /ncr is still a thing.
3) There's a bunch of heavily SEO'd content that's sort of okay but not great, and a bunch of content that's great but hidden.
4) Google really wants you to use natural language queries. So when you're fault-finding a problem you type a question into the search box. This will return many people asking that same question, but often they will not have got an answer. I don't need to be linked to a closed, with no answers, Stack exchange question, or a forum when OP says "never mind, fixed it" with no more details.
5) Google has decided to de-prioritise certain types of link. If you search for torrents Google has chosen to put other stuff in the first few pages. I think I'd prefer it if they just said "nope, we don't do those links" than what they do at the moment. Try searching for pirate versions of Pozner and Dodd's Cross-Examination Science and Techniques and you get a lot of links, but they're all terrible. They all lead to malware infested sites, or sites that are part of a weird complicated network that don't provide any content, but cause you to spend some time finding that out.