One of the most frequently asked questions concerning the Daily Office is: Why are some chapters of Scripture are skipped?
This blog post by Fr. Matthew Brench deals with that question with particular focus on the 2019 Lectionary. It even provides a quick list about what has been omitted in the 2019 Lectionary and links with useful notes.
I think his blog post is useful in understanding some of the issues and factors which are considered when coming up with a lectionary. Also handy are the suggestions on how to make up for the missing readings in the 2019 Lectionary.