I wrote one of the first posts on the MPU Discourse: DEVONthink: stuck at the bottom of the hill
I am still on DT and upgraded to DTP3 and I like the new version. However the the DTTG apps on iOs and iPadOS are in need of some love. They need to make their functions into parameters so they can be used with the new Shortcuts ecosystem. Then we can all whip up our own shortcuts quickly to connect the files to OmniFocus (or Things depending on what time of day) and Calendar.