She owes me a new BS-o-meter
"Today Thunderbird developers spend much of their time responding to changes made in core Mozilla systems and technologies. At the same time, build, Firefox, and platform engineers continue to pay a tax to support Thunderbird."
Excuse me, but there ceased to be a full-time developer working on Thunderbird since some time now. That "tax" must be pretty small. So their finances must be really in the gutter. What did they do with millions upon millions upon millions they received from their deal with Google?
The atrociously high stupidity of matching TB version with FF did not help. Mail clients are like databases: you don't want a new version every five minutes, and if there's a new version, there must be a valid reason to upgrade.
"I believe Thunderbird would thrive best by separating itself from reliance on Mozilla development systems and in some cases, Mozilla technology."
That is one gigantic confession of failure. Of course it's hard for Thunderbird to be "synchronized" with Firefox technologies, because just to figure out what's going on with those is in itself a full-time job. Let me reformulate this in another way:
"Thunderbird would thrive best by separating itself from reliance on" Netscape Communicator 4 technology.