Dreamweaver doesn't replace HTML, it generates HTML. HTML (generally) is the language that web sites are written in - You use DW or FP or another editor as a tool to output the HTML for you, instead of writing the HTML character by character by hand in say, Notepad.
This is what it comes down to. If you don't understand HTML you're going to run into something you can't fix, or can't do, or can't figure out, simply because you don't understand what is going on behind the scenes. IMHO anyone who is going to build sites should learn about HTML aside from whatever editor they choose to use. (look at CSS too)
When I started out I built my first sites in Notepad. Now, I use DWMX + Homesite depending on what I need to do. As tools go, they make it quicker, easier to get what I need to do done.