We switched to the Google recommended text size for the playlists and song lists.

This is the same size used for example in:
Gmail (the sender name and subject line in the message list),
Google Messages (the message preview snippet)
Google Contacts (contact names),
Google Calendar (event titles), etc.

If you find the text to be too small, we recommend increasing the device’s font size in Settings -> Display -> Display size and text -> Font size.