MailChimp’s founders built the company slowly by anticipating customers’ needs
As a regular user of all the main email marketing services:I feel Mailchimp is missing the boat by focusing entirely on email and not offering a way to contact customers via:1. In-app messages
2. SMS 
3. Push notificationsIt's also difficult / impossible to set up advanced automation sequences with it. For example, if Customer X does Y on your site, direct them to another branch with a different sequence.Of course, their main target customers are small businesses so they may not need these advanced features but these customers would benefit tremendously from being able to for example text certain messages to customers instead of only being able to email them.