I've been using TB for many years, at the workplace, at home, on various Windoze nnn systems, and Linux. I've been very happy with it because it can be customized (if you know how), even by my astronomically huge family of fellow idiots (we breed, even faster than Furbeys). I had a similar problem when I held my nose and took the plunge with the 78 update. I was immediately struck my the new look and feel, and my immediate reaction was "Oh God, another pimply faced kid who knows everything but still has no clue as to what good software is". It was reminescent of the MS OS monopoly trials when Gates declared that "the Users want it". (Yes, good software, but not the Borg company that assimilates and corrupts everything.)
Forgive the tirade, but I come from an age where tools to easily transition TB to new systems or different platforms did not exist, so I had to do it the hard way. Before I discuss that - and I did revert to the old (68.10.0 in W10), let me say that this is not for the faint of heart and I thought "Disaster!" many times along the way. I did manage to restore everything successfully to a version of TB that I was happy with. When I say restore, I mean all address books and all old emails in named local directories. If you are looking to perform the same miracle, however, you need to have copies of vital Thunderbird files backed up.
Backups are a problem, but maybe that's because I'm used to doing my own with DOS and xcopy commands. They don't work as well as they used to, and PowerShell is not the answer. W10 and previous W versions have not been able to execute broad "COPY" commands without "abort on error" failures for many years (Microsoft corrupts everything!)
To remedy any TB problems, one needs to be aware that the solution lies outside the capabilities of most people for the reasons stated above.
Let's drill down to the fix:
If you rely on TB automatic updates, maybe the fix has happened and tomorrow everything will be fine.
There are ways to restore old TB releases, but these ARE NOT backward compatible , so the pimply faced kids have won.
Sorry - can't think of any thing else...