What you see is what you get, or WYSIWYG, editing programs allow you to build a website without learning any coding languages. The interface allows you to choose the colors, font, and general design features of the web site and the program then automatically completes the coding for you. As with any tool, there are pros and cons associated with the use of WYSIWYG programs.
WYSIWYG editors are very easy to use. They are great for first time web developers or people who want to experiment with options they do not know enough about to code.
WYSIWYG editors are an excellent way to save time as well. In only a fraction of the time it would take to code an entire web site one of these editing programs can do the job.
WYSIWYG editors allow you to change and update your web site on a regular basis. This allows greater long term design flexibility.
Being proficient in only one or two specific WYSIWYG editors is going to make you less employable than being proficient in a standard coding language such as HTML.
The degree of design control available with most WYSIWYG editors is less than what you could achieve by coding the page yourself.
There are numerous coding irregularities that a WYSIWYG editor will create.
Should you use a WYSIWYG editor?
That depends on what you need it for. If you are designing your own personal website then a WYSIWYG editor is a fine choice. You will be able to get a polished web site in less time and for far less money than it would take for you to either learn a coding language or for you to hire someone to create a page for you.
If you wish to become a professional web designer the WYSIWYG editors can be useful for an initial quick presentation of a concept. However, to snag bigger clients and to appeal to design firms you will need to be able to code as well.