I was thinking for few months about making a multiple topic website, something like an online magazine (I don't know if it's ok to post examples here) with multiple categories, like science, entertainment, nature something in that sense. Do these types of websites even work today, are they at all profitable? The reason I was going for something similar to this is cause I didn't want to go with just one topic, cause I know it might get overwhelming with time in to be just one niche, and I personally actually like these general knowledge types of websites. But, I am really not sure if this is something that is worth of all the work. Would it be better to go with something else?
Well, it depends on your approach and what you perceive as "general," generally if you have a blog you most likely need a niche, a lot of "experienced people in the blogging industry" say that having a general blog is not good for the traffic and it might confuse the search engine. However, if you website idea is like Listverse (check it now I included its link) you may have some success with it, Listevers is all about Top 10 lists ( which is a wide niche) as you can see within "the top 10 lists niche" they included many other topics, horror, mystery, history, and the other categories. You see, it just depends on your idea, with that being said, can you clarify exactly what is your "multiple topic website" main idea? What is about?
General topic ideas would be challenging. You could breakdown your content based on your skills, it would be better if you're passionate about the topic that you're going to create and share. It would drive more value to your site. May we know what topics are you going to create?
Working on a general niche can be problematic especially when you need traffic on your website. Bloggers should have a particular niche so that search engines don't get confused and you get more traffic.