Folks not all the end users of these products are techies. As such some feed back with the latest version of Thunderbird.
The highly touted new look is not good for older folks, the font selection and elimination of the contrast in the background look more modern, but make it difficult to use the product as such many of my colleagues have back versioned and stopped updates.
Perhaps a suggestion to include a method to use the new software features while allowing a user selection on how the product presents itself. In other words let the community select the best interface for each individual.
Again only a suggestion.