This is true, but in fairness when I decided to leave consoles behind for good, I got an Optiplex (755) on Amazon for 80 bucks and slowly upgraded it. It was a tank for me and while it was nowhere near what I have now, it still did me just fine and I was able to enjoy even newer games on it once I added the GPU and upgraded the processor. All in all, I had about $160 invested into it from top to bottom and it was better than a 360/PS3 technologically. My first year on Steam was with that machine and I never had a problem with it other than the limitations. The biggest problem I had with it was the proprietary garbage made it really hard upgrading some parts (i.e. the power supply and had some socket limitations for processor upgrade), finally I gave up when the hard drive started to go and decided to get serious and now use the Optiplex in the garage when Im doing work on my bikes, saves the walk back and forth to the beast to use the internet.
For a toe dip into the pool, a Dell is okay IMO. I would not recommend it whatsoever if you're serious or intend to be serious, but I was hesitant to go headfirst back into PC gaming after being with consoles for almost the entire 360/PS3 generation. I took a small step and I am glad I did. It gave me time to learn exactly what I wanted to be able to do and then was ready to step it up. I sold off the components that would get me some coin (the processor and GPU) and then upgraded.
Other than the hard drive death, the used Dell was a great purchase b/c of what I wanted to do at the time and the thing has been a great utility machine (back to stock parts) in its post-gaming days.