What I fails to understand it's why no one seems to offer the most logic MUE which is essentially offering the full download/sync of all accounts maildirs, like

What I fails to understand it's why no one seems to offer the most logic MUE which is essentially offering the full download/sync of all accounts maildirs, like with OfflineIMAP, than offer powerful local indexing like notmuch/mu with a pre-made UI nice for end users. Slogan: own your own messages, own a local GMail. We have all the code except the UI