Welcome!

CC3 is definitely a program designed for "power users." If you don't have the time and energy to devote to learning it, it's probably better to look for something else. I'd hate to spend money on a program that didn't meet my needs.

I'm not sure you'll be able to find a single program with enough prefab tiles to meet your needs, but you can harvest tiles from a variety of other sources and assemble them in any general-purpose editor like the Gimp. Check out the August entries in the Mapping Challenges forum here for a small assortment of tiles in a variety of styles.

Also, you might take a look at RobA's Dungeon Prettier script for Gimp, which was used to produce his tiles for the aforementioned Challenge. If you can draw a layout in simple black-and-white shapes, the script can automagically turn it into a decent-looking dungeon. It might take a little work setting up the styles (I haven't used it, so I don't know), but I'm sure Rob would be happy to help you with that. You'd still need to drop in furnishings and objects, though.

Another thing to consider is you can slice pieces out of existing maps and use those as your tiles. It will probably take a bit of work to resize pieces of different maps so they fit together, but you'll have the same problem if you use pre-built tiles from two or more different sources.