Now if you have a 'group' or individual you want to communicate with, the messages between said group or person are all combined in one HUGE message. Try going back to find a given message or image you've shared, IF you have the patience to scroll forever, searching everything you've ever 'said' (written) in the past!
A bunch of my DMs just disappeared after this change, and there doesn't appear to be any way to find them.
How anybody could see this as an 'improvement' is beyond me.