Twitter has huge room for growth, at least 10X from where it is. I just don't think they have done enough to figure out what is preventing so many other people to become its frequent user. In my own experience, I find Twitter's newsfeed algorithm pretty bad and completely lacking stickiness. I can easily find stories that would have kept my attention which should have ranked much above. The presentation of content is fairly complex (too many # and @ to parse). Ranking of re-tweets is especially bad. Lot of essential tools are still missing, for example, I can't even search my own tweets effectively. Lot of essential integration is left to 3rd parties (for example, no official Chrome plugin). If you think about it, we communicate a lot like Twitter by using medium of text messages. However text messages lack lot of desirable features (non searchable, history gets purged, hard to create one-off groups etc). Twitter, if done right, can replace text messages and even emails at large extent in addition to social aspects.

I've recently started using Twitter more to stay in touch with deep learning community and I can absolutely see why less tech-savvy non-fan user would turn away after few attempts. I can also see if they can turn this around and grow 10X in terms of DAW/MAU with good product planning.