Andrea is correct. We did make the cards significantly smaller in the later BETA versions. We may reconsider adding the list views again in a minor/major version if it continues to be an area of concern.
The reason card view has been chosen is because of its ability to accommodate all screen sizes (desktop, tablet, mobile). Card views are becoming much more common. If you are familiar with Google Assistant, all based on cards. If your familiar with Cortona on Windows, you will see that they are in cards and it looks exactly the same on the Cortona for Android and iOS.
We have a lot of thought and time into SmarterMail 16.x. More than a year of effort and many rounds with Focus Groups, Alpha Tests and now Beta Testers!