Have a look to the blog post: https://michaelochurch.wordpress.com/2015/06/06/why-agile-and-especially-scrum-are-terrible/
A very interesting read, but I do not agree 100%. Some parts are a little too biased and come out of situations where Scrum is not applied correctly. It is also possible to “plan” refactorings, paying back technical debts and so forth. But, it is always good to read some critics about stuff one does all the time to re-think the own doing.