Maybe, but I find it kinda frustrating that they invested a lot of time in the direct opposite way. Thunderbird had Qt/GTK support in version 102. In the next release, they forced their own theme and moved some elements while removing Qt and GTK support with the nonsensical justification of "we'd have to hardcode every single possible color permutation that the user could theme" when you get the colors from a function. They then locked the threads about this. I assume they did some internal refactoring, but still, it feels frustrating.
(note that the new UI can be customizable to have the inbox be single-row and the mail content be on the bottom)
(also 115 is 102's next release, thunderbird updates the major version number to whatever firefox's is at the time of release)