Yeah, but you see, that is part of the problem. Each browser already has its own style, so you want Tiddlywiki to also have its own style, so that it looks the same across all browsers, but what about those people that use Firefox for example, and don’t like that TIddlywiki is not using the Firefox style that they expect. It is all a matter of personal preference, so Tiddlywiki simply leaves it to the browser you are using to determine the style. Most professional websites online do not use the default styling provided by the browser. They customize it with CSS the way they like. You want Tiddlywiki to customize it to a design that you personally think is “modern” or “aesthetically pleasing”, but who is to say what that is? If they started including styles provided in the core, then where does that end? How many styles, who’s idea of “modern” or “aesthetically pleasing” is going to appease the most people? In the end, they end up with exactly what they have. People designing their own style with CSS and attaching as a class to the object. Ultimately, Tiddlywik is not doing anything other than what ever other web developer on the planet is doing. Designing their site the way they want with CSS. Tiddlywiki in its most basic form, a clean empty.html is as bare bones as you get appearance wise, but it gives you a foundation to build on rather than you developing it from scratch on your own. You have to take the time to style things the way you like. Tiddlywiki is infinitely customizable, unlike other note taking systems that require you to use THEIR style.
Don’t take anything I am saying as an insult, it is just that TIddlywiki can only do so much, without practically writing your notes for you. There is a templating system, access to css classes in all of their widgets, everything they can do to allow you to completely alter the entire visual appearance and functionality to whatever you like. It is better to leave it to the individual than to start bloating the system down with unnecessary personal preferences.