I did not like Rey for the reasons others have already explained: she felt blank, boring, too good too fast, not enough motivation for the things she did etc. For me she just felt completely like a tool...
BUT I think she wasn't the only badly written character in these movies. She got the biggest part, so the flaws in her writing were more obvious but other characters were written purely as tools, too. For example Poe was a really boring characters and in the first movie mostly just a plot device for Finn. Rose? Plot device for Finn. These characters all lack proper character because the writing in these movies is not about building characters but working on moving the plot forward. It's the type of writing that reduces characters into stereotypes or mere actions that they have to perform.
This is the problem with the new movies for me. The OT had it's problems but it managed to give us memorable characters who had personality, personal goals and great flaws. And they had great moments together! It wasn't all about making funny jokes and fast action or dramatic moments. The best moments were often the calm ones, like Leia and Luke talking about their mother.
I feel like they got so stuck on Rey being a hero that they kinda forgot to make her human. To let her be weak and break down, so she can rise up. She's also constantly on the move, so her connection with other characters seem weak and unexplored. I think they didn't plan her well enough and have a clear view in mind about what they want to do with her, which also weakens her character.
Three movies should be long enough to give a character a proper story but I think they failed already with Rey, and the final movie probably cannot salvage her. For me there's nothing I'd want to see from her because there is no proper goal in the distance she has been struggling towards in the previous movies.