Forks are a sign of success.
Thunderbird enjoys regular releases and remains a best-of-breed tool.
Never got on with Thunderbird myself so I can't concur with that. But does have the advantage of being cross-platform.
As for Waterfox, if it's now based on FF 78, I assume this means it using the Quantum engine as well. The reasons for dropping XUL when it happened were more than sound: a very unwieldy codebase and potential for exploitation by malicious add-ons.
However, I don't really think that Mozilla could do much about the decline in market share given the market dominance of Chrome and users' inertia to changing default software, especially on mobile platforms which are now dominant. The number of those that realy want something different is probably pretty small but maybe enough if Vivaldi is anything to go by.
But, personally, despite some irksome UI decisions (today's version wants to give me more colours for some reason) I find the Quantum based Firefox faster and more stable than its predecessor.
Biting the hand that feeds IT
