I think at least to the response to the Browser being complex and ever changing they need to understand the browser is what we may call the “Universal Client” and except when we all had a hard pill to swallow to improve browser security, because of all the malware out there, browsers are thus reliable.
Browsers as a rule are possibly the most reliable backwardly compatible client that exists. After all many different operating systems access the internet through browsers, and it is the browser which is universal in nature.
Now build your apps with backward compatible tiddlywiki and you have a “universal app”, running in a backwardly compatible (mostly) Universal client, both using the same international internet protocols, which themselves are mostly backwardly compatible and need to be so because the WORLD has adopted these standards.
A lot of others will suffer if the standards on which tiddlywiki depends are broken, I would ask why worry about tiddlywiki surviving the end of the world when no one will survive the end of the world.
The fact is tiddlywiki also evolves into the glove it is designed for, in part because many people can depend on it and the worse case scenario, which we already faced once in history, that we called the TiddlyFox Apocalypse you can survive it just by choosing an appropriate browser, and even these can be virtual apps in a sandbox now.
Finally as a tiddlywiki user you have full access to the source code, nothing is hidden, if an incremental change damages it ( unlikely), an incremental fix keeps tiddlywiki going.
None of this is the case with a vast majority of applications that need compiling, have OS dependencies, use one or more programming languages and megabytes of libraries and bespoke platforms, and database demands.
TiddlyWiki is its own platform, document, app, website and software development environment, and did I say all open source?. This places tiddlywiki in an almost unique place in the pantheon of software. Take the Red Pill.