UI Frameworks are not easy and can be as difficult as learning a new programming language. Yet why would you use one? Why bother using something like Semantic UI or any of the other hundreds of frameworks? I would say that it depends on the Framework. Is it easy to use? Does it have a comprehensive tutorial that you can access? Exactly how fast can you pick it up and why would you choose it over the others? Honestly I prefer using raw html and css, it is better documented for the most part and there are more users that are able to help you trouble shoot or there has been someone whose asked the same questions you have. However it was certainly interesting to use Semantic UI.
I think if I learned Semantic UI I would certainly have a different opinion and I will definitely be making more use of it in the future when I can. It certainly has a few things that is better than html and css. For one I think the icons that it provides is certainly helpful. Along with icons I think the buttons are also definitely a plus. I definitely have to learn more about it to become better at it. A big issue I had was being unable to position things the way I wanted to. Another drawback was that IntelliJ (My IDE) was unable to tell me if it was the correct variation or if I was just adding in a meaningless word. An example would be ui borderless menu and ui borderless top menu. Based on Semantic UI reasoning, you would think that there would already a variation using top that places the menu at the top of the page. However I just added in an extension to the class and it doesn’t modify anything. Both ui borderless menu and ui borderless top menu lead to the same menu. Of course I can add in css to make ui borderless top menu be a “top” menu but it seems like something that should be added in.
All in all though I think that there are certainly advantages to using semantic ui and there are definitely something that make it a drawback. All in all though I would say I will continue to use it and I hope that I become better at it. Especially since I have no idea what the keyword fitted does other than resizing a certain way.