As a mapping enthusiast, with no intent of working within professional game design (though I'd like to work on community based mods), I'd have to agree with several points Quakis has raised.
If you want to produce your own content it's far tougher in new engines. Producing textures and models are jobs unto themselves and it's hard to achieve the standards of professionally produced content. Not only is a higher level of technical proficiency required, The time taken to produce these resources is greater.
The cool thing about doing this shit as a hobby is you have complete creative control, you can produce whatever you want, and take as long as you want to do it.