That's more of an issue of you searching. You mention sentiment analysis, for example, but it is a problem that is considered to be solved for years. There is no novelty you could do here besides a bigger model.

Obviously you need to stop looking at what people have done, and start looking at what in their process of doing something they didn't do or did poorly. One such thing is tokenization of text. You can't tell me that it's all figured out.